Hybrid drive caching in a backup system with SSD deletion management

ABSTRACT

Systems and methods can implement one or more intelligent caching algorithms that reduce wear on the SSD and/or to improve caching performance. Such algorithms can improve storage utilization and I/O efficiency by taking into account the write-wearing limitations of the SSD. Accordingly, the systems and methods can cache to the SSD while avoiding writing too frequently to the SSD to increase or attempt to increase the lifespan of the SSD. The systems and methods may, for instance, write data to the SSD once that data has been read from the hard disk or memory multiple times to avoid or attempt to avoid writing data that has been read only once. The systems and methods may also write large chunks of data to the SSD at once instead of a single unit of data at a time. Further, the systems and methods can write to the SSD in a circular fashion.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet of the present applicationare hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND

Businesses worldwide recognize the commercial value of their data andseek reliable, cost-effective ways to protect the information stored ontheir computer networks while minimizing impact on productivity.Protecting information is often part of a routine process that isperformed within an organization. A company might back up criticalcomputing systems such as databases, file servers, web servers, and soon as part of a daily, weekly, or monthly maintenance schedule. Thecompany may similarly protect computing systems used by each of itsemployees, such as those used by an accounting department, marketingdepartment, engineering department, and so forth.

Given the rapidly expanding volume of data under management, companiesalso continue to seek innovative techniques for managing data growth, inaddition to protecting data. For instance, companies often implementmigration techniques for moving data to lower cost storage over time anddata reduction techniques for reducing redundant data, pruning lowerpriority data, etc. Enterprises also increasingly view their stored dataas a valuable asset. Along these lines, customers are looking forsolutions that not only protect and manage, but also leverage theirdata. For instance, solutions providing data analysis capabilities,information management, improved data presentation and access features,and the like, are in increasing demand.

Data storage devices, such as magnetic disk drives, optical disk drives,hybrid drives, and solid state drives are used to store data forsubsequent retrieval. Such devices can employ data caches, which mayinclude high-speed semiconductor memory chips that enable the devices torapidly manage the data and commands received from a host computer.Without caching, all read and write commands from the host computerwould result in an access to the mass storage medium, such as a magneticdisk. Such access may result in significant time latencies due tomechanical positioning of the head relative to the magnetic disk. Bycaching, the storage device can buffer data that is likely to beaccessed by the host computer so that when the data is actuallyaccessed, the data is made available more quickly.

SUMMARY

Certain aspects, advantages and novel features of the inventions aredescribed herein. It is to be understood that not necessarily all suchadvantages may be achieved in accordance with any particular embodimentof the inventions disclosed herein. Thus, the inventions disclosedherein may be embodied or carried out in a manner that achieves orselects one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

According to certain aspects, a method is provided of caching in astorage system comprising a hard disk and a solid-state drive. Themethod can include receiving a first read request to read a first pagefrom a hybrid drive comprising a hard disk and a solid-state drive(SSD). The SSD may operate as a cache for the hard disk and having afaster read speed than the hard disk. The method can include determiningwhether the first page is located in the SSD and, in response todetermining that the first page is not located in the SSD, reading thefirst page from the hard disk, but not caching the first page in the SSDyet to attempt to avoid unnecessarily writing to the SSD should thefirst page not be read again in the near future. This can be in anattempt to reduce wear on the SSD. The method can also include asubsequent read request to read the first page from the hybrid drive. Inresponse to receiving the subsequent read request, the method caninclude reading the first page from the hard disk or from memory if thefirst page is in the memory, and using a processor to mark the firstpage for caching in the SSD while waiting to cache the first page in theSSD until other pages have also been indicated as ready for caching, soas to attempt to avoid wastefully writing individual pages to the SSDand thereby attempt to reduce wear on the SSD. In response todetermining that a predetermined number of pages have been indicated asready for caching, including the first page, the method can furtherinclude writing the first page and the other pages indicated as readyfor caching to the SSD together so as to efficiently write the pagesindicated as ready for caching to the SSD and to attempt to reduce wearon the SSD.

The method can further include first caching the first page in a memorycache in the memory prior to caching the first page in the SSD. Themethod can also include maintaining a hash table in the memory. The hashtable can be configured to map the first page and the other pagesindicated as ready for caching to a storage location in either thememory or the SSD. The first read request and the subsequent readrequest relate to backup operations in some embodiments.

According to additional aspects, a system is disclosed for caching in astorage system comprising a hard disk and a solid-state drive. Thesystem can include a storage driver implemented in a hardware processorcomprising executable instructions configured to: receive a firstrequest to read a first data element from a storage system comprising ahard disk and a solid-state drive (SSD), the SSD operating as a cachefor the hard disk. The storage driver can further be configured to readthe first data element from the hard disk. The storage driver canfurther be configured to receive a second request to read the first dataelement from the storage system. In response to reception of the secondread request, the storage driver can be configured to indicate that thefirst data element is ready for caching in the SSD. The storage drivercan also be configured to determine whether a predetermined quantity ofdata elements have been indicated as ready for caching in addition toand including the first data element. In response to a determinationthat the predetermined quantity of data elements have been indicated asready for caching, the storage driver can be configured to write thedata elements indicated as ready for caching, including the first dataelement, together to the SSD.

The system can further include a hybrid drive in certain embodiments.According to certain aspects, the storage driver can be furtherconfigured to maintain a data structure in the memory. The datastructure can be configured to map the data elements indicated as readyfor caching to a storage location in either the memory or the SSD. Thedata structure can be a hash table indexed at least by data elementidentifier. The storage driver can be further configured to evict thefirst data element from the SSD in response to receiving a write to thefirst data element. The storage driver can be further configured towrite the data elements indicated as ready for caching to the SSD in acircular manner to reduce wear on the SSD.

The storage driver can further configured to cache the first dataelement in the memory prior to writing the data element to the SSD. Thestorage driver can be further configured to evict the first data elementfrom the memory in response to writing the data element to the SSD.

Depending on the embodiment, the quantity of data elements cancorrespond to one or both of size of the data elements and number of thedata elements.

The storage driver can include an interface to one or both of a filesystem and a database, from which the first and second read request arereceived.

According to yet further aspects, a system is described for caching. Thesystem can include a hardware processor configured to perform some orall of the following steps: read a first data element from a hard disk;store a first indication in memory that the first data element is to becached in a solid-state drive (SSD) without actually caching the firstdata element in the SSD; read a second data element from the hard disk;store a second indication in the memory that the second data element isto be cached in the SSD; and subsequent to storage of the secondindication in the memory, cache the first and second data elements inthe SSD.

The hardware processor can be further configured to store the first andsecond indication in a buffer in memory. In such cases, the first andsecond indication can comprise pointers to the first and second dataelements. In some cases, the hardware processor is further configured tocache the first and second data elements in the SSD in response to thebuffer reaching capacity. The hardware processor in some embodiments isconfigured to first cache the first and second data elements in a memorycache prior to caching the first and second data elements in the SSD.The hardware processor can be further configured to cache the first andsecond data elements in the SSD in response to the memory cache reachingcapacity even if the buffer has not reached capacity.

In some embodiments, the hardware processor is configured to evict thefirst data element from the SSD in response to receiving a write to thefirst data element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram illustrating an exemplary informationmanagement system.

FIG. 1B is a detailed view of a primary storage device, a secondarystorage device, and some examples of primary data and secondary copydata.

FIG. 1C is a block diagram of an exemplary information management systemincluding a storage manager, one or more data agents, and one or moremedia agents.

FIG. 1D is a block diagram illustrating a scalable informationmanagement system.

FIG. 1E illustrates certain secondary copy operations according to anexemplary storage policy.

FIGS. 1F-1H are block diagrams illustrating suitable data structuresthat may be employed by the information management system.

FIG. 2 is a block diagram of an example computing system that canimplement intelligent caching using a hybrid drive.

FIG. 3 depicts an example hybrid drive caching process that can beimplemented by the computing system of FIG. 2.

FIG. 4 depicts an example set of data structures that can be used by thecomputing system of FIG. 2.

FIG. 5 depicts an example initial caching process that can beimplemented by the computing system of FIG. 2.

FIG. 6 depicts an example in-hash process that can be implemented by thecomputing system of FIG. 2.

FIG. 7 depicts an example SSD write process that can be implemented bythe computing system of FIG. 2.

FIG. 8 depicts an example write I/O process that can be implemented bythe computing system of FIG. 2.

DETAILED DESCRIPTION

A hybrid drive can include a hard disk and a solid-state drive (SSD)that may be used as a cache for the hard disk. The SSD can cache certaininput/output (I/O) to and from the SSD so that frequently accessed datastored in the hard disk can be accessed more quickly from the SSD. Onereason for using an SSD as a cache instead of replacing a relativelyslower hard disk with faster SSD technology entirely is that flashmemory is more expensive than hard disk technology. Thus, a hybrid drivecan provide a compromise of price versus storage capacity by including ahard disk with large storage capacity and an SSD cache that is fasteryet has smaller storage capacity than the hard disk.

Unfortunately, SSDs have a limited life span in which a limited numberof writes may be performed to each cell or individual unit of memory onthe SSD. Existing logic layers in SSDs can implement wear-levelingalgorithms that attempt to wear SSDs evenly. A wear-leveling algorithmcan, for example, write to different portions of the SSD at differenttimes instead of overwriting the same portion of the SSD multiple timesand thereby ending its life prematurely. However, wear-levelingalgorithms used for SSDs may be insufficient to reduce wear when the SSDis used as a cache. For instance, if every data element that is readfrom the hard disk were cached in the SSD without regard to whether thatelement of data will be used again soon, such writes would reduce thelifespan of the SSD significantly. Further, if a scanning attack isperformed on the computing device, data read once from the hard disk insuch a scanning attack ought not to be cached in the SSD to avoidunnecessarily writing to the SSD. Backup operations can also perform aheavy toll as multiple writes may be applied to the SSD during backup.

Accordingly, embodiments of systems and methods disclosed herein canimplement one or more intelligent caching algorithms to take intoaccount these and other issues to reduce wear on the SSD and/or toimprove caching performance. Such intelligent cache algorithms canimprove storage utilization and I/O efficiency by taking into accountthe write-wearing limitations of the SSD. Accordingly, the systems andmethods can cache to the SSD while avoiding writing too frequently tothe SSD to increase or attempt to increase the lifespan of the SSD. Thesystems and methods may, for instance, write data to the SSD once thatdata has been read from the hard disk or memory multiple times to avoidor attempt to avoid writing data that has been read only once. Thesystems and methods may also write large chunks of data to the SSD atonce instead of a single unit of data at a time. Further, the systemsand methods can write to the SSD in a circular fashion, overwriting theoldest or least recently used data to avoid or attempt to avoidoverwriting the same area of the SSD multiple times in a row.

The systems and methods for intelligent caching described herein mayalso be configured and/or incorporated into information managementsystems such as those described herein in FIGS. 1A-1H.

With the increasing importance of protecting and leveraging data,organizations simply cannot afford to take the risk of losing criticaldata. Moreover, runaway data growth and other modern realities makeprotecting and managing data an increasingly difficult task. There istherefore a need for efficient, powerful, and user-friendly solutionsfor protecting and managing data.

Depending on the size of the organization, there are typically many dataproduction sources which are under the purview of tens, hundreds, oreven thousands of employees or other individuals. In the past,individual employees were sometimes responsible for managing andprotecting their data. A patchwork of hardware and software pointsolutions has been applied in other cases. These solutions were oftenprovided by different vendors and had limited or no interoperability.

Certain embodiments described herein provide systems and methods capableof addressing these and other shortcomings of prior approaches byimplementing unified, organization-wide information management. FIG. 1Ashows one such information management system 100, which generallyincludes combinations of hardware and software configured to protect andmanage data and metadata, which is generated and used by the variouscomputing devices in information management system 100. The organizationthat employs the information management system 100 may be a corporationor other business entity, non-profit organization, educationalinstitution, household, governmental agency, or the like.

Generally, the systems and associated components described herein may becompatible with and/or provide some or all of the functionality of thesystems and corresponding components described in one or more of thefollowing U.S. patents and patent application publications assigned toCommVault Systems, Inc., each of which is hereby incorporated in itsentirety by reference herein:

-   -   U.S. Pat. No. 7,035,880, entitled “Modular Backup and Retrieval        System Used in Conjunction With a Storage Area Network”;    -   U.S. Pat. No. 7,107,298, entitled “System And Method For        Archiving Objects In An Information Store”;    -   U.S. Pat. No. 7,246,207, entitled “System and Method for        Dynamically Performing Storage Operations in a Computer        Network”;    -   U.S. Pat. No. 7,315,923, entitled “System And Method For        Combining Data Streams In Pipelined Storage Operations In A        Storage Network”;    -   U.S. Pat. No. 7,343,453, entitled “Hierarchical Systems and        Methods for Providing a Unified View of Storage Information”;    -   U.S. Pat. No. 7,395,282, entitled “Hierarchical Backup and        Retrieval System”;    -   U.S. Pat. No. 7,529,782, entitled “System and Methods for        Performing a Snapshot and for Restoring Data”;    -   U.S. Pat. No. 7,617,262, entitled “System and Methods for        Monitoring Application Data in a Data Replication System”;    -   U.S. Pat. No. 7,747,579, entitled “Metabase for Facilitating        Data Classification”;    -   U.S. Pat. No. 8,156,086, entitled “Systems And Methods For        Stored Data Verification”;    -   U.S. Pat. No. 8,170,995, entitled “Method and System for Offline        Indexing of Content and Classifying Stored Data”;    -   U.S. Pat. No. 8,229,954, entitled “Managing Copies Of Data”;    -   U.S. Pat. No. 8,230,195, entitled “System And Method For        Performing Auxiliary Storage Operations”;    -   U.S. Pat. No. 8,285,681, entitled “Data Object Store and Server        for a Cloud Storage Environment, Including Data Deduplication        and Data Management Across Multiple Cloud Storage Sites”;    -   U.S. Pat. No. 8,307,177, entitled “Systems And Methods For        Management Of Virtualization Data”;    -   U.S. Pat. No. 8,364,652, entitled “Content-Aligned, Block-Based        Deduplication”;    -   U.S. Pat. No. 8,578,120, entitled “Block-Level Single        Instancing”;    -   U.S. Pat. Pub. No. 2006/0224846, entitled “System and Method to        Support Single Instance Storage Operations”;    -   U.S. Pat. Pub. No. 2009/0319534, entitled “Application-Aware and        Remote Single Instance Data Management”;    -   U.S. Pat. Pub. No. 2012/0150818, entitled “Client-Side        Repository in a Networked Deduplicated Storage System”; and    -   U.S. Pat. Pub. No. 2012/0150826, entitled “Distributed        Deduplicated Storage System”.

The information management system 100 can include a variety of differentcomputing devices. For instance, as will be described in greater detailherein, the information management system 100 can include one or moreclient computing devices 102 and secondary storage computing devices106.

Computing devices can include, without limitation, one or more:workstations, personal computers, desktop computers, or other types ofgenerally fixed computing systems such as mainframe computers andminicomputers. Other computing devices can include mobile or portablecomputing devices, such as one or more laptops, tablet computers,personal data assistants, mobile phones (such as smartphones), and othermobile or portable computing devices such as embedded computers, set topboxes, vehicle-mounted devices, wearable computers, etc. Computingdevices can include servers, such as mail servers, file servers,database servers, and web servers.

In some cases, a computing device includes virtualized and/or cloudcomputing resources. For instance, one or more virtual machines may beprovided to the organization by a third-party cloud service vendor. Or,in some embodiments, computing devices can include one or more virtualmachine(s) running on a physical host computing device (or “hostmachine”) operated by the organization. As one example, the organizationmay use one virtual machine as a database server and another virtualmachine as a mail server, both virtual machines operating on the samehost machine.

A virtual machine includes an operating system and associated virtualresources, and is hosted simultaneously with another operating system ona physical host computer (or host machine). A hypervisor (typicallysoftware, and also known in the art as a virtual machine monitor or avirtual machine manager or “VMM”) sits between the virtual machine andthe hardware of the physical host machine. One example of hypervisor asvirtualization software is ESX Server, by VMware, Inc. of Palo Alto,Calif.; other examples include Microsoft Virtual Server and MicrosoftWindows Server Hyper-V, both by Microsoft Corporation of Redmond, Wash.,and Sun xVM by Oracle America Inc. of Santa Clara, Calif. In someembodiments, the hypervisor may be firmware or hardware or a combinationof software and/or firmware and/or hardware.

The hypervisor provides to each virtual operating system virtualresources, such as a virtual processor, virtual memory, a virtualnetwork device, and a virtual disk. Each virtual machine has one or morevirtual disks. The hypervisor typically stores the data of virtual disksin files on the file system of the physical host machine, called virtualmachine disk files (in the case of VMware virtual servers) or virtualhard disk image files (in the case of Microsoft virtual servers). Forexample, VMware's ESX Server provides the Virtual Machine File System(VMFS) for the storage of virtual machine disk files. A virtual machinereads data from and writes data to its virtual disk much the same waythat an actual physical machine reads data from and writes data to anactual disk.

Examples of techniques for implementing information managementtechniques in a cloud computing environment are described in U.S. Pat.No. 8,285,681, which is incorporated by reference herein. Examples oftechniques for implementing information management techniques in avirtualized computing environment are described in U.S. Pat. No.8,307,177, also incorporated by reference herein.

The information management system 100 can also include a variety ofstorage devices, including primary storage devices 104 and secondarystorage devices 108, for example. Storage devices can generally be ofany suitable type including, without limitation, disk drives, hard-diskarrays, semiconductor memory (e.g., solid state storage devices),network attached storage (NAS) devices, tape libraries or othermagnetic, non-tape storage devices, optical media storage devices,DNA/RNA-based memory technology, combinations of the same, and the like.In some embodiments, storage devices can form part of a distributed filesystem. In some cases, storage devices are provided in a cloud (e.g., aprivate cloud or one operated by a third-party vendor). A storage devicein some cases comprises a disk array or portion thereof.

The illustrated information management system 100 includes one or moreclient computing device 102 having at least one application 110executing thereon, and one or more primary storage devices 104 storingprimary data 112. The client computing device(s) 102 and the primarystorage devices 104 may generally be referred to in some cases as aprimary storage subsystem 117. A computing device in an informationmanagement system 100 that has a data agent 142 installed and operatingon it is generally referred to as a client computing device 102 (or, inthe context of a component of the information management system 100simply as a “client”).

Depending on the context, the term “information management system” canrefer to generally all of the illustrated hardware and softwarecomponents. Or, in other instances, the term may refer to only a subsetof the illustrated components.

For instance, in some cases, the information management system 100generally refers to a combination of specialized components used toprotect, move, manage, manipulate, analyze, and/or process data andmetadata generated by the client computing devices 102. However, theinformation management system 100 in some cases does not include theunderlying components that generate and/or store the primary data 112,such as the client computing devices 102 themselves, the applications110 and operating system operating on the client computing devices 102,and the primary storage devices 104. As an example, “informationmanagement system” may sometimes refer to one or more of the followingcomponents and corresponding data structures: storage managers, dataagents, and media agents. These components will be described in furtherdetail below.

Client Computing Devices

There are typically a variety of sources in an organization that producedata to be protected and managed. As just one illustrative example, in acorporate environment such data sources can be employee workstations andcompany servers such as a mail server, a web server, a database server,a transaction server, or the like. In the information management system100, the data generation sources include the one or more clientcomputing devices 102.

The client computing devices 102 may include any of the types ofcomputing devices described above, without limitation, and in some casesthe client computing devices 102 are associated with one or more usersand/or corresponding user accounts, of employees or other individuals.

The information management system 100 generally addresses and handlesthe data management and protection needs for the data generated by theclient computing devices 102. However, the use of this term does notimply that the client computing devices 102 cannot be “servers” in otherrespects. For instance, a particular client computing device 102 may actas a server with respect to other devices, such as other clientcomputing devices 102. As just a few examples, the client computingdevices 102 can include mail servers, file servers, database servers,and web servers.

Each client computing device 102 may have one or more applications 110(e.g., software applications) executing thereon which generate andmanipulate the data that is to be protected from loss and managed. Theapplications 110 generally facilitate the operations of an organization(or multiple affiliated organizations), and can include, withoutlimitation, mail server applications (e.g., Microsoft Exchange Server),file server applications, mail client applications (e.g., MicrosoftExchange Client), database applications (e.g., SQL, Oracle, SAP, LotusNotes Database), word processing applications (e.g., Microsoft Word),spreadsheet applications, financial applications, presentationapplications, graphics and/or video applications, browser applications,mobile applications, entertainment applications, and so on.

The client computing devices 102 can have at least one operating system(e.g., Microsoft Windows, Mac OS X, iOS, IBM z/OS, Linux, otherUnix-based operating systems, etc.) installed thereon, which may supportor host one or more file systems and other applications 110.

The client computing devices 102 and other components in informationmanagement system 100 can be connected to one another via one or morecommunication pathways 114. For example, a first communication pathway114 may connect (or communicatively couple) client computing device 102and secondary storage computing device 106; a second communicationpathway 114 may connect storage manager 140 and client computing device102; and a third communication pathway 114 may connect storage manager140 and secondary storage computing device 106, etc. (see, e.g., FIG. 1Aand FIG. 1C). The communication pathways 114 can include one or morenetworks or other connection types including one or more of thefollowing, without limitation: the Internet, a wide area network (WAN),a local area network (LAN), a Storage Area Network (SAN), a FibreChannel connection, a Small Computer System Interface (SCSI) connection,a virtual private network (VPN), a token ring or TCP/IP based network,an intranet network, a point-to-point link, a cellular network, awireless data transmission system, a two-way cable system, aninteractive kiosk network, a satellite network, a broadband network, abaseband network, a neural network, a mesh network, an ad hoc network,other appropriate wired, wireless, or partially wired/wireless computeror telecommunications networks, combinations of the same or the like.The communication pathways 114 in some cases may also includeapplication programming interfaces (APIs) including, e.g., cloud serviceprovider APIs, virtual machine management APIs, and hosted serviceprovider APIs. The underlying infrastructure of communication paths 114may be wired and/or wireless, analog and/or digital, or any combinationthereof; and the facilities used may be private, public, third-partyprovided, or any combination thereof, without limitation.

Primary Data and Exemplary Primary Storage Devices

Primary data 112 according to some embodiments is production data orother “live” data generated by the operating system and/or applications110 operating on a client computing device 102. The primary data 112 isgenerally stored on the primary storage device(s) 104 and is organizedvia a file system supported by the client computing device 102. Forinstance, the client computing device(s) 102 and correspondingapplications 110 may create, access, modify, write, delete, andotherwise use primary data 112. In some cases, some or all of theprimary data 112 can be stored in cloud storage resources (e.g., primarystorage device 104 may be a cloud-based resource).

Primary data 112 is generally in the native format of the sourceapplication 110. According to certain aspects, primary data 112 is aninitial or first (e.g., created before any other copies or before atleast one other copy) stored copy of data generated by the sourceapplication 110. Primary data 112 in some cases is created substantiallydirectly from data generated by the corresponding source applications110.

The primary storage devices 104 storing the primary data 112 may berelatively fast and/or expensive technology (e.g., a disk drive, ahard-disk array, solid state memory, etc.). In addition, primary data112 may be highly changeable and/or may be intended for relatively shortterm retention (e.g., hours, days, or weeks).

According to some embodiments, the client computing device 102 canaccess primary data 112 from the primary storage device 104 by makingconventional file system calls via the operating system. Primary data112 may include structured data (e.g., database files), unstructureddata (e.g., documents), and/or semi-structured data. Some specificexamples are described below with respect to FIG. 1B.

It can be useful in performing certain tasks to organize the primarydata 112 into units of different granularities. In general, primary data112 can include files, directories, file system volumes, data blocks,extents, or any other hierarchies or organizations of data objects. Asused herein, a “data object” can refer to both (1) any file that iscurrently addressable by a file system or that was previouslyaddressable by the file system (e.g., an archive file) and (2) a subsetof such a file (e.g., a data block).

As will be described in further detail, it can also be useful inperforming certain functions of the information management system 100 toaccess and modify metadata within the primary data 112. Metadatagenerally includes information about data objects or characteristicsassociated with the data objects. For simplicity herein, it is to beunderstood that, unless expressly stated otherwise, any reference toprimary data 112 generally also includes its associated metadata, butreferences to the metadata do not include the primary data.

Metadata can include, without limitation, one or more of the following:the data owner (e.g., the client or user that generates the data), thelast modified time (e.g., the time of the most recent modification ofthe data object), a data object name (e.g., a file name), a data objectsize (e.g., a number of bytes of data), information about the content(e.g., an indication as to the existence of a particular search term),user-supplied tags, to/from information for email (e.g., an emailsender, recipient, etc.), creation date, file type (e.g., format orapplication type), last accessed time, application type (e.g., type ofapplication that generated the data object), location/network (e.g., acurrent, past or future location of the data object and network pathwaysto/from the data object), geographic location (e.g., GPS coordinates),frequency of change (e.g., a period in which the data object ismodified), business unit (e.g., a group or department that generates,manages or is otherwise associated with the data object), aginginformation (e.g., a schedule, such as a time period, in which the dataobject is migrated to secondary or long term storage), boot sectors,partition layouts, file location within a file folder directorystructure, user permissions, owners, groups, access control lists[ACLs]), system metadata (e.g., registry information), combinations ofthe same or other similar information related to the data object.

In addition to metadata generated by or related to file systems andoperating systems, some of the applications 110 and/or other componentsof the information management system 100 maintain indices of metadatafor data objects, e.g., metadata associated with individual emailmessages. Thus, each data object may be associated with correspondingmetadata. The use of metadata to perform classification and otherfunctions is described in greater detail below.

Each of the client computing devices 102 are generally associated withand/or in communication with one or more of the primary storage devices104 storing corresponding primary data 112. A client computing device102 may be considered to be “associated with” or “in communication with”a primary storage device 104 if it is capable of one or more of: routingand/or storing data (e.g., primary data 112) to the particular primarystorage device 104, coordinating the routing and/or storing of data tothe particular primary storage device 104, retrieving data from theparticular primary storage device 104, coordinating the retrieval ofdata from the particular primary storage device 104, and modifyingand/or deleting data retrieved from the particular primary storagedevice 104.

The primary storage devices 104 can include any of the different typesof storage devices described above, or some other kind of suitablestorage device. The primary storage devices 104 may have relatively fastI/O times and/or are relatively expensive in comparison to the secondarystorage devices 108. For example, the information management system 100may generally regularly access data and metadata stored on primarystorage devices 104, whereas data and metadata stored on the secondarystorage devices 108 is accessed relatively less frequently.

Primary storage device 104 may be dedicated or shared. In some cases,each primary storage device 104 is dedicated to an associated clientcomputing device 102. For instance, a primary storage device 104 in oneembodiment is a local disk drive of a corresponding client computingdevice 102. In other cases, one or more primary storage devices 104 canbe shared by multiple client computing devices 102, e.g., via a networksuch as in a cloud storage implementation. As one example, a primarystorage device 104 can be a disk array shared by a group of clientcomputing devices 102, such as one of the following types of diskarrays: EMC Clariion, EMC Symmetrix, EMC Celerra, Dell EqualLogic, IBMXIV, NetApp FAS, HP EVA, and HP 3PAR.

The information management system 100 may also include hosted services(not shown), which may be hosted in some cases by an entity other thanthe organization that employs the other components of the informationmanagement system 100. For instance, the hosted services may be providedby various online service providers to the organization. Such serviceproviders can provide services including social networking services,hosted email services, or hosted productivity applications or otherhosted applications). Hosted services may include software-as-a-service(SaaS), platform-as-a-service (PaaS), application service providers(ASPS), cloud services, or other mechanisms for delivering functionalityvia a network. As it provides services to users, each hosted service maygenerate additional data and metadata under management of theinformation management system 100, e.g., as primary data 112. In somecases, the hosted services may be accessed using one of the applications110. As an example, a hosted mail service may be accessed via browserrunning on a client computing device 102. The hosted services may beimplemented in a variety of computing environments. In some cases, theyare implemented in an environment having a similar arrangement to theinformation management system 100, where various physical and logicalcomponents are distributed over a network.

Secondary Copies and Exemplary Secondary Storage Devices

The primary data 112 stored on the primary storage devices 104 may becompromised in some cases, such as when an employee deliberately oraccidentally deletes or overwrites primary data 112 during their normalcourse of work. Or the primary storage devices 104 can be damaged, lost,or otherwise corrupted. For recovery and/or regulatory compliancepurposes, it is therefore useful to generate copies of the primary data112. Accordingly, the information management system 100 includes one ormore secondary storage computing devices 106 and one or more secondarystorage devices 108 configured to create and store one or more secondarycopies 116 of the primary data 112 and associated metadata. Thesecondary storage computing devices 106 and the secondary storagedevices 108 may sometimes be referred to as a secondary storagesubsystem 118.

Creation of secondary copies 116 can help in search and analysis effortsand meet other information management goals, such as: restoring dataand/or metadata if an original version (e.g., of primary data 112) islost (e.g., by deletion, corruption, or disaster); allowingpoint-in-time recovery; complying with regulatory data retention andelectronic discovery (e-discovery) requirements; reducing utilizedstorage capacity; facilitating organization and search of data;improving user access to data files across multiple computing devicesand/or hosted services; and implementing data retention policies.

The client computing devices 102 access or receive primary data 112 andcommunicate the data, e.g., over one or more communication pathways 114,for storage in the secondary storage device(s) 108.

A secondary copy 116 can comprise a separate stored copy of applicationdata that is derived from one or more earlier-created, stored copies(e.g., derived from primary data 112 or another secondary copy 116).Secondary copies 116 can include point-in-time data, and may be intendedfor relatively long-term retention (e.g., weeks, months or years),before some or all of the data is moved to other storage or isdiscarded.

In some cases, a secondary copy 116 is a copy of application datacreated and stored subsequent to at least one other stored instance(e.g., subsequent to corresponding primary data 112 or to anothersecondary copy 116), in a different storage device than at least oneprevious stored copy, and/or remotely from at least one previous storedcopy. In some other cases, secondary copies can be stored in the samestorage device as primary data 112 and/or other previously storedcopies. For example, in one embodiment a disk array capable ofperforming hardware snapshots stores primary data 112 and creates andstores hardware snapshots of the primary data 112 as secondary copies116. Secondary copies 116 may be stored in relatively slow and/or lowcost storage (e.g., magnetic tape). A secondary copy 116 may be storedin a backup or archive format, or in some other format different thanthe native source application format or other primary data format.

In some cases, secondary copies 116 are indexed so users can browse andrestore at another point in time. After creation of a secondary copy 116representative of certain primary data 112, a pointer or other locationindicia (e.g., a stub) may be placed in primary data 112, or beotherwise associated with primary data 112 to indicate the currentlocation on the secondary storage device(s) 108 of secondary copy 116.

Since an instance of a data object or metadata in primary data 112 maychange over time as it is modified by an application 110 (or hostedservice or the operating system), the information management system 100may create and manage multiple secondary copies 116 of a particular dataobject or metadata, each representing the state of the data object inprimary data 112 at a particular point in time. Moreover, since aninstance of a data object in primary data 112 may eventually be deletedfrom the primary storage device 104 and the file system, the informationmanagement system 100 may continue to manage point-in-timerepresentations of that data object, even though the instance in primarydata 112 no longer exists.

For virtualized computing devices the operating system and otherapplications 110 of the client computing device(s) 102 may executewithin or under the management of virtualization software (e.g., a VMM),and the primary storage device(s) 104 may comprise a virtual diskcreated on a physical storage device. The information management system100 may create secondary copies 116 of the files or other data objectsin a virtual disk file and/or secondary copies 116 of the entire virtualdisk file itself (e.g., of an entire .vmdk file).

Secondary copies 116 may be distinguished from corresponding primarydata 112 in a variety of ways, some of which will now be described.First, as discussed, secondary copies 116 can be stored in a differentformat (e.g., backup, archive, or other non-native format) than primarydata 112. For this or other reasons, secondary copies 116 may not bedirectly useable by the applications 110 of the client computing device102, e.g., via standard system calls or otherwise without modification,processing, or other intervention by the information management system100.

Secondary copies 116 are also in some embodiments stored on a secondarystorage device 108 that is inaccessible to the applications 110 runningon the client computing devices 102 (and/or hosted services). Somesecondary copies 116 may be “offline copies,” in that they are notreadily available (e.g., not mounted to tape or disk). Offline copiescan include copies of data that the information management system 100can access without human intervention (e.g., tapes within an automatedtape library, but not yet mounted in a drive), and copies that theinformation management system 100 can access only with at least somehuman intervention (e.g., tapes located at an offsite storage site).

The Use of Intermediate Devices for Creating Secondary Copies

Creating secondary copies can be a challenging task. For instance, therecan be hundreds or thousands of client computing devices 102 continuallygenerating large volumes of primary data 112 to be protected. Also,there can be significant overhead involved in the creation of secondarycopies 116. Moreover, secondary storage devices 108 may be specialpurpose components, and interacting with them can require specializedintelligence.

In some cases, the client computing devices 102 interact directly withthe secondary storage device 108 to create the secondary copies 116.However, in view of the factors described above, this approach cannegatively impact the ability of the client computing devices 102 toserve the applications 110 and produce primary data 112. Further, theclient computing devices 102 may not be optimized for interaction withthe secondary storage devices 108.

Thus, in some embodiments, the information management system 100includes one or more software and/or hardware components which generallyact as intermediaries between the client computing devices 102 and thesecondary storage devices 108. In addition to off-loading certainresponsibilities from the client computing devices 102, theseintermediate components can provide other benefits. For instance, asdiscussed further below with respect to FIG. 1D, distributing some ofthe work involved in creating secondary copies 116 can enhancescalability.

The intermediate components can include one or more secondary storagecomputing devices 106 as shown in FIG. 1A and/or one or more mediaagents, which can be software modules operating on correspondingsecondary storage computing devices 106 (or other appropriate computingdevices). Media agents are discussed below (e.g., with respect to FIGS.1C-1E).

The secondary storage computing device(s) 106 can comprise any of thecomputing devices described above, without limitation. In some cases,the secondary storage computing device(s) 106 include specializedhardware and/or software componentry for interacting with the secondarystorage devices 108.

To create a secondary copy 116 involving the copying of data from theprimary storage subsystem 117 to the secondary storage subsystem 118,the client computing device 102 in some embodiments communicates theprimary data 112 to be copied (or a processed version thereof) to thedesignated secondary storage computing device 106, via the communicationpathway 114. The secondary storage computing device 106 in turn conveysthe received data (or a processed version thereof) to the secondarystorage device 108. In some such configurations, the communicationpathway 114 between the client computing device 102 and the secondarystorage computing device 106 comprises a portion of a LAN, WAN or SAN.In other cases, at least some client computing devices 102 communicatedirectly with the secondary storage devices 108 (e.g., via Fibre Channelor SCSI connections). In some other cases, one or more secondary copies116 are created from existing secondary copies, such as in the case ofan auxiliary copy operation, described in greater detail below.

Exemplary Primary Data and an Exemplary Secondary Copy

FIG. 1B is a detailed view showing some specific examples of primarydata stored on the primary storage device(s) 104 and secondary copy datastored on the secondary storage device(s) 108, with other components inthe system removed for the purposes of illustration. Stored on theprimary storage device(s) 104 are primary data objects including wordprocessing documents 119A-B, spreadsheets 120, presentation documents122, video files 124, image files 126, email mailboxes 128 (andcorresponding email messages 129A-C), html/xml or other types of markuplanguage files 130, databases 132 and corresponding tables or other datastructures 133A-133C).

Some or all primary data objects are associated with correspondingmetadata (e.g., “Meta1-11”), which may include file system metadataand/or application specific metadata. Stored on the secondary storagedevice(s) 108 are secondary copy data objects 134A-C which may includecopies of or otherwise represent corresponding primary data objects andmetadata.

As shown, the secondary copy data objects 134A-C can individuallyrepresent more than one primary data object. For example, secondary copydata object 134A represents three separate primary data objects 133C,122, and 129C (represented as 133C′, 122′, and 129C′, respectively, andaccompanied by the corresponding metadata Meta11, Meta3, and Meta8,respectively). Moreover, as indicated by the prime mark (′), a secondarycopy object may store a representation of a primary data object and/ormetadata differently than the original format, e.g., in a compressed,encrypted, deduplicated, or other modified format. Likewise, secondarydata object 134B represents primary data objects 120, 133B, and 119A as120′, 133B′, and 119A′, respectively and accompanied by correspondingmetadata Meta2, Meta10, and Meta1, respectively. Also, secondary dataobject 134C represents primary data objects 133A, 1198, and 129A as133A′, 119B′, and 129A′, respectively, accompanied by correspondingmetadata Meta9, Meta5, and Meta6, respectively.

Exemplary Information Management System Architecture

The information management system 100 can incorporate a variety ofdifferent hardware and software components, which can in turn beorganized with respect to one another in many different configurations,depending on the embodiment. There are critical design choices involvedin specifying the functional responsibilities of the components and therole of each component in the information management system 100. Forinstance, as will be discussed, such design choices can impactperformance as well as the adaptability of the information managementsystem 100 to data growth or other changing circumstances.

FIG. 1C shows an information management system 100 designed according tothese considerations and which includes: storage manager 140, acentralized storage and/or information manager that is configured toperform certain control functions, one or more data agents 142 executingon the client computing device(s) 102 configured to process primary data112, and one or more media agents 144 executing on the one or moresecondary storage computing devices 106 for performing tasks involvingthe secondary storage devices 108. While distributing functionalityamongst multiple computing devices can have certain advantages, in othercontexts it can be beneficial to consolidate functionality on the samecomputing device. As such, in various other embodiments, one or more ofthe components shown in FIG. 1C as being implemented on separatecomputing devices are implemented on the same computing device. In oneconfiguration, a storage manager 140, one or more data agents 142, andone or more media agents 144 are all implemented on the same computingdevice. In another embodiment, one or more data agents 142 and one ormore media agents 144 are implemented on the same computing device,while the storage manager 140 is implemented on a separate computingdevice, etc. without limitation.

Storage Manager

As noted, the number of components in the information management system100 and the amount of data under management can be quite large. Managingthe components and data is therefore a significant task, and a task thatcan grow in an often unpredictable fashion as the quantity of componentsand data scale to meet the needs of the organization. For these andother reasons, according to certain embodiments, responsibility forcontrolling the information management system 100, or at least asignificant portion of that responsibility, is allocated to the storagemanager 140. By distributing control functionality in this manner, thestorage manager 140 can be adapted independently according to changingcircumstances. Moreover, a computing device for hosting the storagemanager 140 can be selected to best suit the functions of the storagemanager 140. These and other advantages are described in further detailbelow with respect to FIG. 1D.

The storage manager 140 may be a software module or other application,which, in some embodiments operates in conjunction with one or moreassociated data structures, e.g., a dedicated database (e.g., managementdatabase 146). In some embodiments, storage manager 140 is a computingdevice comprising circuitry for executing computer instructions andperforms the functions described herein. The storage manager generallyinitiates, performs, coordinates and/or controls storage and otherinformation management operations performed by the informationmanagement system 100, e.g., to protect and control the primary data 112and secondary copies 116 of data and metadata. In general, storagemanager 100 may be said to manage information management system 100,which includes managing the constituent components, e.g., data agentsand media agents, etc.

As shown by the dashed arrowed lines 114 in FIG. 1C, the storage manager140 may communicate with and/or control some or all elements of theinformation management system 100, such as the data agents 142 and mediaagents 144. Thus, in certain embodiments, control information originatesfrom the storage manager 140 and status reporting is transmitted tostorage manager 140 by the various managed components, whereas payloaddata and payload metadata is generally communicated between the dataagents 142 and the media agents 144 (or otherwise between the clientcomputing device(s) 102 and the secondary storage computing device(s)106), e.g., at the direction of and under the management of the storagemanager 140. Control information can generally include parameters andinstructions for carrying out information management operations, suchas, without limitation, instructions to perform a task associated withan operation, timing information specifying when to initiate a taskassociated with an operation, data path information specifying whatcomponents to communicate with or access in carrying out an operation,and the like. Payload data, on the other hand, can include the actualdata involved in the storage operation, such as content data written toa secondary storage device 108 in a secondary copy operation. Payloadmetadata can include any of the types of metadata described herein, andmay be written to a storage device along with the payload content data(e.g., in the form of a header).

In other embodiments, some information management operations arecontrolled by other components in the information management system 100(e.g., the media agent(s) 144 or data agent(s) 142), instead of or incombination with the storage manager 140.

According to certain embodiments, the storage manager 140 provides oneor more of the following functions:

-   -   initiating execution of secondary copy operations;    -   managing secondary storage devices 108 and inventory/capacity of        the same;    -   reporting, searching, and/or classification of data in the        information management system 100;    -   allocating secondary storage devices 108 for secondary storage        operations;    -   monitoring completion of and providing status reporting related        to secondary storage operations;    -   tracking age information relating to secondary copies 116,        secondary storage devices 108, and comparing the age information        against retention guidelines;    -   tracking movement of data within the information management        system 100;    -   tracking logical associations between components in the        information management system 100;    -   protecting metadata associated with the information management        system 100; and    -   implementing operations management functionality.

The storage manager 140 may maintain a database 146 (or “storage managerdatabase 146” or “management database 146”) of management-related dataand information management policies 148. The database 146 may include amanagement index 150 (or “index 150”) or other data structure thatstores logical associations between components of the system, userpreferences and/or profiles (e.g., preferences regarding encryption,compression, or deduplication of primary or secondary copy data,preferences regarding the scheduling, type, or other aspects of primaryor secondary copy or other operations, mappings of particularinformation management users or user accounts to certain computingdevices or other components, etc.), management tasks, mediacontainerization, or other useful data. For example, the storage manager140 may use the index 150 to track logical associations between mediaagents 144 and secondary storage devices 108 and/or movement of datafrom primary storage devices 104 to secondary storage devices 108. Forinstance, the index 150 may store data associating a client computingdevice 102 with a particular media agent 144 and/or secondary storagedevice 108, as specified in an information management policy 148 (e.g.,a storage policy, which is defined in more detail below).

Administrators and other people may be able to configure and initiatecertain information management operations on an individual basis. Butwhile this may be acceptable for some recovery operations or otherrelatively less frequent tasks, it is often not workable forimplementing on-going organization-wide data protection and management.Thus, the information management system 100 may utilize informationmanagement policies 148 for specifying and executing informationmanagement operations (e.g., on an automated basis). Generally, aninformation management policy 148 can include a data structure or otherinformation source that specifies a set of parameters (e.g., criteriaand rules) associated with storage or other information managementoperations.

The storage manager database 146 may maintain the information managementpolicies 148 and associated data, although the information managementpolicies 148 can be stored in any appropriate location. For instance, aninformation management policy 148 such as a storage policy may be storedas metadata in a media agent database 152 or in a secondary storagedevice 108 (e.g., as an archive copy) for use in restore operations orother information management operations, depending on the embodiment.Information management policies 148 are described further below.

According to certain embodiments, the storage manager database 146comprises a relational database (e.g., an SQL database) for trackingmetadata, such as metadata associated with secondary copy operations(e.g., what client computing devices 102 and corresponding data wereprotected). This and other metadata may additionally be stored in otherlocations, such as at the secondary storage computing devices 106 or onthe secondary storage devices 108, allowing data recovery without theuse of the storage manager 140 in some cases.

As shown, the storage manager 140 may include a jobs agent 156, a userinterface 158, and a management agent 154, all of which may beimplemented as interconnected software modules or application programs.

The jobs agent 156 in some embodiments initiates, controls, and/ormonitors the status of some or all storage or other informationmanagement operations previously performed, currently being performed,or scheduled to be performed by the information management system 100.For instance, the jobs agent 156 may access information managementpolicies 148 to determine when and how to initiate and control secondarycopy and other information management operations, as will be discussedfurther.

The user interface 158 may include information processing and displaysoftware, such as a graphical user interface (“GUI”), an applicationprogram interface (“API”), or other interactive interface(s) throughwhich users and system processes can retrieve information about thestatus of information management operations (e.g., storage operations)or issue instructions to the information management system 100 and itsconstituent components. Via the user interface 158, users may optionallyissue instructions to the components in the information managementsystem 100 regarding performance of storage and recovery operations. Forexample, a user may modify a schedule concerning the number of pendingsecondary copy operations. As another example, a user may employ the GUIto view the status of pending storage operations or to monitor thestatus of certain components in the information management system 100(e.g., the amount of capacity left in a storage device).

An “information management cell” (or “storage operation cell” or “cell”)may generally include a logical and/or physical grouping of acombination of hardware and software components associated withperforming information management operations on electronic data,typically one storage manager 140 and at least one client computingdevice 102 (comprising data agent(s) 142) and at least one media agent144. For instance, the components shown in FIG. 1C may together form aninformation management cell. Multiple cells may be organizedhierarchically. With this configuration, cells may inherit propertiesfrom hierarchically superior cells or be controlled by other cells inthe hierarchy (automatically or otherwise). Alternatively, in someembodiments, cells may inherit or otherwise be associated withinformation management policies, preferences, information managementmetrics, or other properties or characteristics according to theirrelative position in a hierarchy of cells. Cells may also be delineatedand/or organized hierarchically according to function, geography,architectural considerations, or other factors useful or desirable inperforming information management operations. A first cell may representa geographic segment of an enterprise, such as a Chicago office, and asecond cell may represent a different geographic segment, such as a NewYork office. Other cells may represent departments within a particularoffice. Where delineated by function, a first cell may perform one ormore first types of information management operations (e.g., one or morefirst types of secondary or other copies), and a second cell may performone or more second types of information management operations (e.g., oneor more second types of secondary or other copies).

The storage manager 140 may also track information that permits it toselect, designate, or otherwise identify content indices, deduplicationdatabases, or similar databases or resources or data sets within itsinformation management cell (or another cell) to be searched in responseto certain queries. Such queries may be entered by the user viainteraction with the user interface 158. In general, the managementagent 154 allows multiple information management cells to communicatewith one another. For example, the information management system 100 insome cases may be one information management cell of a network ofmultiple cells adjacent to one another or otherwise logically related ina WAN or LAN. With this arrangement, the cells may be connected to oneanother through respective management agents 154.

For instance, the management agent 154 can provide the storage manager140 with the ability to communicate with other components within theinformation management system 100 (and/or other cells within a largerinformation management system) via network protocols and applicationprogramming interfaces (“APIs”) including, e.g., HTTP, HTTPS, FTP, REST,virtualization software APIs, cloud service provider APIs, and hostedservice provider APIs. Inter-cell communication and hierarchy isdescribed in greater detail in e.g., U.S. Pat. Nos. 7,747,579 and7,343,453, which are incorporated by reference herein.

Data Agents

As discussed, a variety of different types of applications 110 canoperate on a given client computing device 102, including operatingsystems, database applications, e-mail applications, and virtualmachines, just to name a few. And, as part of the process of creatingand restoring secondary copies 116, the client computing devices 102 maybe tasked with processing and preparing the primary data 112 from thesevarious different applications 110. Moreover, the nature of theprocessing/preparation can differ across clients and application types,e.g., due to inherent structural and formatting differences amongapplications 110.

The one or more data agent(s) 142 are therefore advantageouslyconfigured in some embodiments to assist in the performance ofinformation management operations based on the type of data that isbeing protected, at a client-specific and/or application-specific level.

The data agent 142 may be a software module or component that isgenerally responsible for managing, initiating, or otherwise assistingin the performance of information management operations in informationmanagement system 100, generally as directed by storage manager 140. Forinstance, the data agent 142 may take part in performing data storageoperations such as the copying, archiving, migrating, and/or replicatingof primary data 112 stored in the primary storage device(s) 104. Thedata agent 142 may receive control information from the storage manager140, such as commands to transfer copies of data objects, metadata, andother payload data to the media agents 144.

In some embodiments, a data agent 142 may be distributed between theclient computing device 102 and storage manager 140 (and any otherintermediate components) or may be deployed from a remote location orits functions approximated by a remote process that performs some or allof the functions of data agent 142. In addition, a data agent 142 mayperform some functions provided by a media agent 144, or may performother functions such as encryption and deduplication.

As indicated, each data agent 142 may be specialized for a particularapplication 110, and the system can employ multiple application-specificdata agents 142, each of which may perform information managementoperations (e.g., perform backup, migration, and data recovery)associated with a different application 110. For instance, differentindividual data agents 142 may be designed to handle Microsoft Exchangedata, Lotus Notes data, Microsoft Windows file system data, MicrosoftActive Directory Objects data, SQL Server data, SharePoint data, Oracledatabase data, SAP database data, virtual machines and/or associateddata, and other types of data.

A file system data agent, for example, may handle data files and/orother file system information. If a client computing device 102 has twoor more types of data, a specialized data agent 142 may be used for eachdata type to copy, archive, migrate, and restore the client computingdevice 102 data. For example, to backup, migrate, and/or restore all ofthe data on a Microsoft Exchange server, the client computing device 102may use a Microsoft Exchange Mailbox data agent 142 to back up theExchange mailboxes, a Microsoft Exchange Database data agent 142 to backup the Exchange databases, a Microsoft Exchange Public Folder data agent142 to back up the Exchange Public Folders, and a Microsoft Windows FileSystem data agent 142 to back up the file system of the client computingdevice 102. In such embodiments, these specialized data agents 142 maybe treated as four separate data agents 142 even though they operate onthe same client computing device 102.

Other embodiments may employ one or more generic data agents 142 thatcan handle and process data from two or more different applications 110,or that can handle and process multiple data types, instead of or inaddition to using specialized data agents 142. For example, one genericdata agent 142 may be used to back up, migrate and restore MicrosoftExchange Mailbox data and Microsoft Exchange Database data while anothergeneric data agent may handle Microsoft Exchange Public Folder data andMicrosoft Windows File System data.

Each data agent 142 may be configured to access data and/or metadatastored in the primary storage device(s) 104 associated with the dataagent 142 and process the data as appropriate. For example, during asecondary copy operation, the data agent 142 may arrange or assemble thedata and metadata into one or more files having a certain format (e.g.,a particular backup or archive format) before transferring the file(s)to a media agent 144 or other component. The file(s) may include a listof files or other metadata. Each data agent 142 can also assist inrestoring data or metadata to primary storage devices 104 from asecondary copy 116. For instance, the data agent 142 may operate inconjunction with the storage manager 140 and one or more of the mediaagents 144 to restore data from secondary storage device(s) 108.

Media Agents

As indicated above with respect to FIG. 1A, off-loading certainresponsibilities from the client computing devices 102 to intermediatecomponents such as the media agent(s) 144 can provide a number ofbenefits including improved client computing device 102 operation,faster secondary copy operation performance, and enhanced scalability.In one specific example which will be discussed below in further detail,the media agent 144 can act as a local cache of copied data and/ormetadata that it has stored to the secondary storage device(s) 108,providing improved restore capabilities.

Generally speaking, a media agent 144 may be implemented as a softwaremodule that manages, coordinates, and facilitates the transmission ofdata, as directed by the storage manager 140, between a client computingdevice 102 and one or more secondary storage devices 108. Whereas thestorage manager 140 controls the operation of the information managementsystem 100, the media agent 144 generally provides a portal to secondarystorage devices 108. For instance, other components in the systeminteract with the media agents 144 to gain access to data stored on thesecondary storage devices 108, whether it be for the purposes ofreading, writing, modifying, or deleting data. Moreover, as will bedescribed further, media agents 144 can generate and store informationrelating to characteristics of the stored data and/or metadata, or cangenerate and store other types of information that generally providesinsight into the contents of the secondary storage devices 108.

Media agents 144 can comprise separate nodes in the informationmanagement system 100 (e.g., nodes that are separate from the clientcomputing devices 102, storage manager 140, and/or secondary storagedevices 108). In general, a node within the information managementsystem 100 can be a logically and/or physically separate component, andin some cases is a component that is individually addressable orotherwise identifiable. In addition, each media agent 144 may operate ona dedicated secondary storage computing device 106 in some cases, whilein other embodiments a plurality of media agents 144 operate on the samesecondary storage computing device 106.

A media agent 144 (and corresponding media agent database 152) may beconsidered to be “associated with” a particular secondary storage device108 if that media agent 144 is capable of one or more of: routing and/orstoring data to the particular secondary storage device 108,coordinating the routing and/or storing of data to the particularsecondary storage device 108, retrieving data from the particularsecondary storage device 108, coordinating the retrieval of data from aparticular secondary storage device 108, and modifying and/or deletingdata retrieved from the particular secondary storage device 108.

While media agent(s) 144 are generally associated with one or moresecondary storage devices 108, one or more media agents 144 in certainembodiments are physically separate from the secondary storage devices108. For instance, the media agents 144 may operate on secondary storagecomputing devices 106 having different housings or packages than thesecondary storage devices 108. In one example, a media agent 144operates on a first server computer and is in communication with asecondary storage device(s) 108 operating in a separate, rack-mountedRAID-based system.

Where the information management system 100 includes multiple mediaagents 144 (see, e.g., FIG. 1D), a first media agent 144 may providefailover functionality for a second, failed media agent 144. Inaddition, media agents 144 can be dynamically selected for storageoperations to provide load balancing. Failover and load balancing aredescribed in greater detail below.

In operation, a media agent 144 associated with a particular secondarystorage device 108 may instruct the secondary storage device 108 toperform an information management operation. For instance, a media agent144 may instruct a tape library to use a robotic arm or other retrievalmeans to load or eject a certain storage media, and to subsequentlyarchive, migrate, or retrieve data to or from that media, e.g., for thepurpose of restoring the data to a client computing device 102. Asanother example, a secondary storage device 108 may include an array ofhard disk drives or solid state drives organized in a RAIDconfiguration, and the media agent 144 may forward a logical unit number(LUN) and other appropriate information to the array, which uses thereceived information to execute the desired storage operation. The mediaagent 144 may communicate with a secondary storage device 108 via asuitable communications link, such as a SCSI or Fiber Channel link.

As shown, each media agent 144 may maintain an associated media agentdatabase 152. The media agent database 152 may be stored in a disk orother storage device (not shown) that is local to the secondary storagecomputing device 106 on which the media agent 144 operates. In othercases, the media agent database 152 is stored remotely from thesecondary storage computing device 106.

The media agent database 152 can include, among other things, an index153 (see, e.g., FIG. 1C), which comprises information generated duringsecondary copy operations and other storage or information managementoperations. The index 153 provides a media agent 144 or other componentwith a fast and efficient mechanism for locating secondary copies 116 orother data stored in the secondary storage devices 108. In some cases,the index 153 does not form a part of and is instead separate from themedia agent database 152.

A media agent index 153 or other data structure associated with theparticular media agent 144 may include information about the storeddata. For instance, for each secondary copy 116, the index 153 mayinclude metadata such as a list of the data objects (e.g.,files/subdirectories, database objects, mailbox objects, etc.), a pathto the secondary copy 116 on the corresponding secondary storage device108, location information indicating where the data objects are storedin the secondary storage device 108, when the data objects were createdor modified, etc. Thus, the index 153 includes metadata associated withthe secondary copies 116 that is readily available for use withouthaving to be first retrieved from the secondary storage device 108. Inyet further embodiments, some or all of the information in index 153 mayinstead or additionally be stored along with the secondary copies ofdata in a secondary storage device 108. In some embodiments, thesecondary storage devices 108 can include sufficient information toperform a “bare metal restore”, where the operating system of a failedclient computing device 102 or other restore target is automaticallyrebuilt as part of a restore operation.

Because the index 153 maintained in the media agent database 152 mayoperate as a cache, it can also be referred to as “an index cache.” Insuch cases, information stored in the index cache 153 typicallycomprises data that reflects certain particulars about storageoperations that have occurred relatively recently. After some triggeringevent, such as after a certain period of time elapses, or the indexcache 153 reaches a particular size, the index cache 153 may be copiedor migrated to a secondary storage device(s) 108. This information mayneed to be retrieved and uploaded back into the index cache 153 orotherwise restored to a media agent 144 to facilitate retrieval of datafrom the secondary storage device(s) 108. In some embodiments, thecached information may include format or containerization informationrelated to archives or other files stored on the storage device(s) 108.In this manner, the index cache 153 allows for accelerated restores.

In some alternative embodiments the media agent 144 generally acts as acoordinator or facilitator of storage operations between clientcomputing devices 102 and corresponding secondary storage devices 108,but does not actually write the data to the secondary storage device108. For instance, the storage manager 140 (or the media agent 144) mayinstruct a client computing device 102 and secondary storage device 108to communicate with one another directly. In such a case the clientcomputing device 102 transmits the data directly or via one or moreintermediary components to the secondary storage device 108 according tothe received instructions, and vice versa. In some such cases, the mediaagent 144 may still receive, process, and/or maintain metadata relatedto the storage operations. Moreover, in these embodiments, the payloaddata can flow through the media agent 144 for the purposes of populatingthe index cache 153 maintained in the media agent database 152, but notfor writing to the secondary storage device 108.

The media agent 144 and/or other components such as the storage manager140 may in some cases incorporate additional functionality, such as dataclassification, content indexing, deduplication, encryption,compression, and the like. Further details regarding these and otherfunctions are described below.

Distributed, Scalable Architecture

As described, certain functions of the information management system 100can be distributed amongst various physical and/or logical components inthe system. For instance, one or more of the storage manager 140, dataagents 142, and media agents 144 may operate on computing devices thatare physically separate from one another. This architecture can providea number of benefits.

For instance, hardware and software design choices for each distributedcomponent can be targeted to suit its particular function. The secondarycomputing devices 106 on which the media agents 144 operate can betailored for interaction with associated secondary storage devices 108and provide fast index cache operation, among other specific tasks.Similarly, the client computing device(s) 102 can be selected toeffectively service the applications 110 thereon, in order toefficiently produce and store primary data 112.

Moreover, in some cases, one or more of the individual components in theinformation management system 100 can be distributed to multiple,separate computing devices. As one example, for large file systems wherethe amount of data stored in the management database 146 is relativelylarge, the database 146 may be migrated to or otherwise reside on aspecialized database server (e.g., an SQL server) separate from a serverthat implements the other functions of the storage manager 140. Thisdistributed configuration can provide added protection because thedatabase 146 can be protected with standard database utilities (e.g.,SQL log shipping or database replication) independent from otherfunctions of the storage manager 140. The database 146 can beefficiently replicated to a remote site for use in the event of adisaster or other data loss at the primary site. Or the database 146 canbe replicated to another computing device within the same site, such asto a higher performance machine in the event that a storage manager hostdevice can no longer service the needs of a growing informationmanagement system 100.

The distributed architecture also provides both scalability andefficient component utilization. FIG. 1D shows an embodiment of theinformation management system 100 including a plurality of clientcomputing devices 102 and associated data agents 142 as well as aplurality of secondary storage computing devices 106 and associatedmedia agents 144.

Additional components can be added or subtracted based on the evolvingneeds of the information management system 100. For instance, dependingon where bottlenecks are identified, administrators can add additionalclient computing devices 102, secondary storage computing devices 106(and corresponding media agents 144), and/or secondary storage devices108. Moreover, where multiple fungible components are available, loadbalancing can be implemented to dynamically address identifiedbottlenecks. As an example, the storage manager 140 may dynamicallyselect which media agents 144 and/or secondary storage devices 108 touse for storage operations based on a processing load analysis of themedia agents 144 and/or secondary storage devices 108, respectively.

Moreover, each client computing device 102 in some embodiments cancommunicate with, among other components, any of the media agents 144,e.g., as directed by the storage manager 140. And each media agent 144may be able to communicate with, among other components, any of thesecondary storage devices 108, e.g., as directed by the storage manager140. Thus, operations can be routed to the secondary storage devices 108in a dynamic and highly flexible manner, to provide load balancing,failover, and the like. Further examples of scalable systems capable ofdynamic storage operations, and of systems capable of performing loadbalancing and fail over are provided in U.S. Pat. No. 7,246,207, whichis incorporated by reference herein.

In alternative configurations, certain components are not distributedand may instead reside and execute on the same computing device. Forexample, in some embodiments, one or more data agents 142 and thestorage manager 140 operate on the same client computing device 102. Inanother embodiment, one or more data agents 142 and one or more mediaagents 144 operate on a single computing device.

Exemplary Types of Information Management Operations

In order to protect and leverage stored data, the information managementsystem 100 can be configured to perform a variety of informationmanagement operations. As will be described, these operations cangenerally include secondary copy and other data movement operations,processing and data manipulation operations, analysis, reporting, andmanagement operations. The operations described herein may be performedon any type of computing device, e.g., between two computers connectedvia a LAN, to a mobile client telecommunications device connected to aserver via a WLAN, to any manner of client computing device coupled to acloud storage target, etc., without limitation.

Data Movement Operations

Data movement operations according to certain embodiments are generallyoperations that involve the copying or migration of data (e.g., payloaddata) between different locations in the information management system100 in an original/native and/or one or more different formats. Forexample, data movement operations can include operations in which storeddata is copied, migrated, or otherwise transferred from one or morefirst storage devices to one or more second storage devices, such asfrom primary storage device(s) 104 to secondary storage device(s) 108,from secondary storage device(s) 108 to different secondary storagedevice(s) 108, from secondary storage devices 108 to primary storagedevices 104, or from primary storage device(s) 104 to different primarystorage device(s) 104.

Data movement operations can include by way of example, backupoperations, archive operations, information lifecycle managementoperations such as hierarchical storage management operations,replication operations (e.g., continuous data replication operations),snapshot operations, deduplication or single-instancing operations,auxiliary copy operations, and the like. As will be discussed, some ofthese operations involve the copying, migration or other movement ofdata, without actually creating multiple, distinct copies. Nonetheless,some or all of these operations are referred to as “copy” operations forsimplicity.

Backup Operations

A backup operation creates a copy of a version of data (e.g., one ormore files or other data units) in primary data 112 at a particularpoint in time. Each subsequent backup copy may be maintainedindependently of the first. Further, a backup copy in some embodimentsis generally stored in a form that is different than the native format,e.g., a backup format. This can be in contrast to the version in primarydata 112 from which the backup copy is derived, and which may instead bestored in a native format of the source application(s) 110. In variouscases, backup copies can be stored in a format in which the data iscompressed, encrypted, deduplicated, and/or otherwise modified from theoriginal application format. For example, a backup copy may be stored ina backup format that facilitates compression and/or efficient long-termstorage.

Backup copies can have relatively long retention periods as compared toprimary data 112, and may be stored on media with slower retrieval timesthan primary data 112 and certain other types of secondary copies 116.On the other hand, backups may have relatively shorter retention periodsthan some other types of secondary copies 116, such as archive copies(described below). Backups may sometimes be stored at an offsitelocation.

Backup operations can include full backups, differential backups,incremental backups, “synthetic full” backups, and/or creating a“reference copy.” A full backup (or “standard full backup”) in someembodiments is generally a complete image of the data to be protected.However, because full backup copies can consume a relatively largeamount of storage, it can be useful to use a full backup copy as abaseline and only store changes relative to the full backup copy forsubsequent backup copies.

For instance, a differential backup operation (or cumulative incrementalbackup operation) tracks and stores changes that have occurred since thelast full backup. Differential backups can grow quickly in size, but canprovide relatively efficient restore times because a restore can becompleted in some cases using only the full backup copy and the latestdifferential copy.

An incremental backup operation generally tracks and stores changessince the most recent backup copy of any type, which can greatly reducestorage utilization. In some cases, however, restore times can berelatively long in comparison to full or differential backups becausecompleting a restore operation may involve accessing a full backup inaddition to multiple incremental backups.

Synthetic full backups generally consolidate data without directlybacking up data from the client computing device. A synthetic fullbackup is created from the most recent full backup (i.e., standard orsynthetic) and subsequent incremental and/or differential backups. Theresulting synthetic full backup is identical to what would have beencreated had the last backup for the subclient been a standard fullbackup. Unlike standard full, incremental, and differential backups, asynthetic full backup does not actually transfer data from a clientcomputer to the backup media, because it operates as a backupconsolidator. A synthetic full backup extracts the index data of eachparticipating subclient. Using this index data and the previously backedup user data images, it builds new full backup images, one for eachsubclient. The new backup images consolidate the index and user datastored in the related incremental, differential, and previous fullbackups, in some embodiments creating an archive file at the subclientlevel.

Any of the above types of backup operations can be at the volume-level,file-level, or block-level. Volume level backup operations generallyinvolve the copying of a data volume (e.g., a logical disk or partition)as a whole. In a file-level backup, the information management system100 may generally track changes to individual files, and includes copiesof files in the backup copy. In the case of a block-level backup, filesare broken into constituent blocks, and changes are tracked at theblock-level. Upon restore, the information management system 100reassembles the blocks into files in a transparent fashion.

Far less data may actually be transferred and copied to the secondarystorage devices 108 during a file-level copy than a volume-level copy.Likewise, a block-level copy may involve the transfer of less data thana file-level copy, resulting in faster execution times. However,restoring a relatively higher-granularity copy can result in longerrestore times. For instance, when restoring a block-level copy, theprocess of locating constituent blocks can sometimes result in longerrestore times as compared to file-level backups. Similar to backupoperations, the other types of secondary copy operations describedherein can also be implemented at either the volume-level, file-level,or block-level.

For example, in some embodiments, a reference copy may comprisecopy(ies) of selected objects from backed up data, typically to helporganize data by keeping contextual information from multiple sourcestogether, and/or help retain specific data for a longer period of time,such as for legal hold needs. A reference copy generally maintains dataintegrity, and when the data is restored, it may be viewed in the sameformat as the source data. In some embodiments, a reference copy isbased on a specialized client, individual subclient and associatedinformation management policies (e.g., storage policy, retention policy,etc.) that are administered within information management system 100.

Archive Operations

Because backup operations generally involve maintaining a version of thecopied data in primary data 112 and also maintaining backup copies insecondary storage device(s) 108, they can consume significant storagecapacity. To help reduce storage consumption, an archive operationaccording to certain embodiments creates a secondary copy 116 by bothcopying and removing source data. Or, seen another way, archiveoperations can involve moving some or all of the source data to thearchive destination. Thus, data satisfying criteria for removal (e.g.,data of a threshold age or size) may be removed from source storage. Thesource data may be primary data 112 or a secondary copy 116, dependingon the situation. As with backup copies, archive copies can be stored ina format in which the data is compressed, encrypted, deduplicated,and/or otherwise modified from the format of the original application orsource copy. In addition, archive copies may be retained for relativelylong periods of time (e.g., years) and, in some cases, are neverdeleted. Archive copies are generally retained for longer periods oftime than backup copies, for example. In certain embodiments, archivecopies may be made and kept for extended periods in order to meetcompliance regulations.

Moreover, when primary data 112 is archived, in some cases thecorresponding primary data 112 or a portion thereof is deleted whencreating the archive copy. Thus, archiving can serve the purpose offreeing up space in the primary storage device(s) 104 and easing thedemand on computational resources on client computing device 102.Similarly, when a secondary copy 116 is archived, the secondary copy 116may be deleted, and an archive copy can therefore serve the purpose offreeing up space in secondary storage device(s) 108. In contrast, sourcecopies often remain intact when creating backup copies. Examples ofcompatible data archiving operations are provided in U.S. Pat. No.7,107,298, which is incorporated by reference herein.

Snapshot Operations

Snapshot operations can provide a relatively lightweight, efficientmechanism for protecting data. From an end-user viewpoint, a snapshotmay be thought of as an “instant” image of the primary data 112 at agiven point in time, and may include state and/or status informationrelative to an application that creates/manages the primary data 112. Inone embodiment, a snapshot may generally capture the directory structureof an object in primary data 112 such as a file or volume or other dataset at a particular moment in time and may also preserve file attributesand contents. A snapshot in some cases is created relatively quickly,e.g., substantially instantly, using a minimum amount of file space, butmay still function as a conventional file system backup.

A “hardware snapshot” (or “hardware-based snapshot”) operation can be asnapshot operation where a target storage device (e.g., a primarystorage device 104 or a secondary storage device 108) performs thesnapshot operation in a self-contained fashion, substantiallyindependently, using hardware, firmware and/or software operating on thestorage device itself. For instance, the storage device may be capableof performing snapshot operations upon request, generally withoutintervention or oversight from any of the other components in theinformation management system 100. In this manner, hardware snapshotscan off-load other components of information management system 100 fromprocessing involved in snapshot creation and management.

A “software snapshot” (or “software-based snapshot”) operation, on theother hand, can be a snapshot operation in which one or more othercomponents in information management system 100 (e.g., client computingdevices 102, data agents 142, etc.) implement a software layer thatmanages the snapshot operation via interaction with the target storagedevice. For instance, the component executing the snapshot managementsoftware layer may derive a set of pointers and/or data that representsthe snapshot. The snapshot management software layer may then transmitthe same to the target storage device, along with appropriateinstructions for writing the snapshot.

Some types of snapshots do not actually create another physical copy ofall the data as it existed at the particular point in time, but maysimply create pointers that are able to map files and directories tospecific memory locations (e.g., to specific disk blocks) where the dataresides, as it existed at the particular point in time. For example, asnapshot copy may include a set of pointers derived from the file systemor from an application. In some other cases, the snapshot may be createdat the block-level, such that creation of the snapshot occurs withoutawareness of the file system. Each pointer points to a respective storeddata block, so that collectively, the set of pointers reflect thestorage location and state of the data object (e.g., file(s) orvolume(s) or data set(s)) at a particular point in time when thesnapshot copy was created.

An initial snapshot may use only a small amount of disk space needed torecord a mapping or other data structure representing or otherwisetracking the blocks that correspond to the current state of the filesystem. Additional disk space is usually required only when files anddirectories are modified later on. Furthermore, when files are modified,typically only the pointers which map to blocks are copied, not theblocks themselves. In some embodiments, for example in the case of“copy-on-write” snapshots, when a block changes in primary storage, theblock is copied to secondary storage or cached in primary storage beforethe block is overwritten in primary storage, and the pointer to thatblock is changed to reflect the new location of that block. The snapshotmapping of file system data may also be updated to reflect the changedblock(s) at that particular point in time. In some other cases, asnapshot includes a full physical copy of all or substantially all ofthe data represented by the snapshot. Further examples of snapshotoperations are provided in U.S. Pat. No. 7,529,782, which isincorporated by reference herein.

A snapshot copy in many cases can be made quickly and withoutsignificantly impacting primary computing resources because largeamounts of data need not be copied or moved. In some embodiments, asnapshot may exist as a virtual file system, parallel to the actual filesystem. Users in some cases gain read-only access to the record of filesand directories of the snapshot. By electing to restore primary data 112from a snapshot taken at a given point in time, users may also returnthe current file system to the state of the file system that existedwhen the snapshot was taken.

Replication Operations

Another type of secondary copy operation is a replication operation.Some types of secondary copies 116 are used to periodically captureimages of primary data 112 at particular points in time (e.g., backups,archives, and snapshots). However, it can also be useful for recoverypurposes to protect primary data 112 in a more continuous fashion, byreplicating the primary data 112 substantially as changes occur. In somecases a replication copy can be a mirror copy, for instance, wherechanges made to primary data 112 are mirrored or substantiallyimmediately copied to another location (e.g., to secondary storagedevice(s) 108). By copying each write operation to the replication copy,two storage systems are kept synchronized or substantially synchronizedso that they are virtually identical at approximately the same time.Where entire disk volumes are mirrored, however, mirroring can requiresignificant amount of storage space and utilizes a large amount ofprocessing resources.

According to some embodiments storage operations are performed onreplicated data that represents a recoverable state, or “known goodstate” of a particular application running on the source system. Forinstance, in certain embodiments, known good replication copies may beviewed as copies of primary data 112. This feature allows the system todirectly access, copy, restore, backup or otherwise manipulate thereplication copies as if the data were the “live” primary data 112. Thiscan reduce access time, storage utilization, and impact on sourceapplications 110, among other benefits. Based on known good stateinformation, the information management system 100 can replicatesections of application data that represent a recoverable state ratherthan rote copying of blocks of data. Examples of compatible replicationoperations (e.g., continuous data replication) are provided in U.S. Pat.No. 7,617,262, which is incorporated by reference herein.

Deduplication/Single-Instancing Operations

Another type of data movement operation is deduplication orsingle-instance storage, which is useful to reduce the amount ofnon-primary data. For instance, some or all of the above-describedsecondary storage operations can involve deduplication in some fashion.New data is read, broken down into portions (e.g., sub-file levelblocks, files, etc.) of a selected granularity, compared with blocksthat are already in secondary storage, and only the new blocks arestored. Blocks that already exist are represented as pointers to thealready stored data.

In order to streamline the comparison process, the informationmanagement system 100 may calculate and/or store signatures (e.g.,hashes or cryptographically unique IDs) corresponding to the individualdata blocks in a database and compare the signatures instead ofcomparing entire data blocks. In some cases, only a single instance ofeach element is stored, and deduplication operations may therefore bereferred to interchangeably as “single-instancing” operations. Dependingon the implementation, however, deduplication or single-instancingoperations can store more than one instance of certain data blocks, butnonetheless significantly reduce data redundancy. Depending on theembodiment, deduplication blocks can be of fixed or variable length.Using variable length blocks can provide enhanced deduplication byresponding to changes in the data stream, but can involve complexprocessing. In some cases, the information management system 100utilizes a technique for dynamically aligning deduplication blocks(e.g., fixed-length blocks) based on changing content in the datastream, as described in U.S. Pat. No. 8,364,652, which is incorporatedby reference herein.

The information management system 100 can perform deduplication in avariety of manners at a variety of locations in the informationmanagement system 100. For instance, in some embodiments, theinformation management system 100 implements “target-side” deduplicationby deduplicating data (e.g., secondary copies 116) stored in thesecondary storage devices 108. In some such cases, the media agents 144are generally configured to manage the deduplication process. Forinstance, one or more of the media agents 144 maintain a correspondingdeduplication database that stores deduplication information (e.g.,datablock signatures). Examples of such a configuration are provided inU.S. Pat. Pub. No. 2012/0150826, which is incorporated by referenceherein. Instead of or in combination with “target-side” deduplication,deduplication can also be performed on the “source-side” (or“client-side”), e.g., to reduce the amount of traffic between the mediaagents 144 and the client computing device(s) 102 and/or reduceredundant data stored in the primary storage devices 104. According tovarious implementations, one or more of the storage devices of thetarget-side and/or source-side of an operation can be cloud-basedstorage devices. Thus, the target-side and/or source-side deduplicationcan be cloud-based deduplication. In particular, as discussedpreviously, the storage manager 140 may communicate with othercomponents within the information management system 100 via networkprotocols and cloud service provider APIs to facilitate cloud-baseddeduplication/single instancing. Examples of such deduplicationtechniques are provided in U.S. Pat. Pub. No. 2012/0150818, which isincorporated by reference herein. Some other compatiblededuplication/single instancing techniques are described in U.S. Pat.Pub. Nos. 2006/0224846 and 2009/0319534, which are incorporated byreference herein.

Information Lifecycle Management and Hierarchical Storage ManagementOperations

In some embodiments, files and other data over their lifetime move frommore expensive, quick access storage to less expensive, slower accessstorage. Operations associated with moving data through various tiers ofstorage are sometimes referred to as information lifecycle management(ILM) operations.

One type of ILM operation is a hierarchical storage management (HSM)operation. A HSM operation is generally an operation for automaticallymoving data between classes of storage devices, such as betweenhigh-cost and low-cost storage devices. For instance, an HSM operationmay involve movement of data from primary storage devices 104 tosecondary storage devices 108, or between tiers of secondary storagedevices 108. With each tier, the storage devices may be progressivelyrelatively cheaper, have relatively slower access/restore times, etc.For example, movement of data between tiers may occur as data becomesless important over time.

In some embodiments, an HSM operation is similar to an archive operationin that creating an HSM copy may (though not always) involve deletingsome of the source data, e.g., according to one or more criteria relatedto the source data. For example, an HSM copy may include data fromprimary data 112 or a secondary copy 116 that is larger than a givensize threshold or older than a given age threshold and that is stored ina backup format.

Often, and unlike some types of archive copies, HSM data that is removedor aged from the source is replaced by a logical reference pointer orstub. The reference pointer or stub can be stored in the primary storagedevice 104 (or other source storage device, such as a secondary storagedevice 108) to replace the deleted source data and to point to orotherwise indicate the new location in a secondary storage device 108.

According to one example, files are generally moved between higher andlower cost storage depending on how often the files are accessed. When auser requests access to the HSM data that has been removed or migrated,the information management system 100 uses the stub to locate the dataand may make recovery of the data appear transparent, even though theHSM data may be stored at a location different from other source data.In this manner, the data appears to the user (e.g., in file systembrowsing windows and the like) as if it still resides in the sourcelocation (e.g., in a primary storage device 104). The stub may alsoinclude some metadata associated with the corresponding data, so that afile system and/or application can provide some information about thedata object and/or a limited-functionality version (e.g., a preview) ofthe data object.

An HSM copy may be stored in a format other than the native applicationformat (e.g., where the data is compressed, encrypted, deduplicated,and/or otherwise modified from the original native application format).In some cases, copies which involve the removal of data from sourcestorage and the maintenance of stub or other logical referenceinformation on source storage may be referred to generally as “on-linearchive copies”. On the other hand, copies which involve the removal ofdata from source storage without the maintenance of stub or otherlogical reference information on source storage may be referred to as“off-line archive copies”. Examples of HSM and ILM techniques areprovided in U.S. Pat. No. 7,343,453, which is incorporated by referenceherein.

Auxiliary Copy and Disaster Recovery Operations

An auxiliary copy is generally a copy operation in which a copy iscreated of an existing secondary copy 116. For instance, an initialsecondary copy 116 may be generated using or otherwise be derived fromprimary data 112 (or other data residing in the secondary storagesubsystem 118), whereas an auxiliary copy is generated from the initialsecondary copy 116. Auxiliary copies can be used to create additionalstandby copies of data and may reside on different secondary storagedevices 108 than the initial secondary copies 116. Thus, auxiliarycopies can be used for recovery purposes if initial secondary copies 116become unavailable. Exemplary compatible auxiliary copy techniques aredescribed in further detail in U.S. Pat. No. 8,230,195, which isincorporated by reference herein.

The information management system 100 may also perform disaster recoveryoperations that make or retain disaster recovery copies, often assecondary, high-availability disk copies. The information managementsystem 100 may create secondary disk copies and store the copies atdisaster recovery locations using auxiliary copy or replicationoperations, such as continuous data replication technologies. Dependingon the particular data protection goals, disaster recovery locations canbe remote from the client computing devices 102 and primary storagedevices 104, remote from some or all of the secondary storage devices108, or both.

Data Analysis, Reporting, and Management Operations

Data analysis, reporting, and management operations can be differentthan data movement operations in that they do not necessarily involvethe copying, migration or other transfer of data (e.g., primary data 112or secondary copies 116) between different locations in the system. Forinstance, data analysis operations may involve processing (e.g., offlineprocessing) or modification of already stored primary data 112 and/orsecondary copies 116. However, in some embodiments data analysisoperations are performed in conjunction with data movement operations.Some data analysis operations include content indexing operations andclassification operations which can be useful in leveraging the dataunder management to provide enhanced search and other features. Otherdata analysis operations such as compression and encryption can providedata reduction and security benefits, respectively.

Classification Operations/Content Indexing

In some embodiments, the information management system 100 analyzes andindexes characteristics, content, and metadata associated with theprimary data 112 and/or secondary copies 116. The content indexing canbe used to identify files or other data objects having pre-definedcontent (e.g., user-defined keywords or phrases, other keywords/phrasesthat are not defined by a user, etc.), and/or metadata (e.g., emailmetadata such as “to”, “from”, “cc”, “bcc”, attachment name, receivedtime, etc.).

The information management system 100 generally organizes and cataloguesthe results in a content index, which may be stored within the mediaagent database 152, for example. The content index can also include thestorage locations of (or pointer references to) the indexed data in theprimary data 112 or secondary copies 116, as appropriate. The resultsmay also be stored, in the form of a content index database orotherwise, elsewhere in the information management system 100 (e.g., inthe primary storage devices 104, or in the secondary storage device108). Such index data provides the storage manager 140 or anothercomponent with an efficient mechanism for locating primary data 112and/or secondary copies 116 of data objects that match particularcriteria.

For instance, search criteria can be specified by a user through userinterface 158 of the storage manager 140. In some cases, the informationmanagement system 100 analyzes data and/or metadata in secondary copies116 to create an “off-line” content index, without significantlyimpacting the performance of the client computing devices 102. Dependingon the embodiment, the system can also implement “on-line” contentindexing, e.g., of primary data 112. Examples of compatible contentindexing techniques are provided in U.S. Pat. No. 8,170,995, which isincorporated by reference herein.

One or more components can be configured to scan data and/or associatedmetadata for classification purposes to populate a database (or otherdata structure) of information, which can be referred to as a “dataclassification database” or a “metabase”. Depending on the embodiment,the data classification database(s) can be organized in a variety ofdifferent ways, including centralization, logical sub-divisions, and/orphysical sub-divisions. For instance, one or more centralized dataclassification databases may be associated with different subsystems ortiers within the information management system 100. As an example, theremay be a first centralized metabase associated with the primary storagesubsystem 117 and a second centralized metabase associated with thesecondary storage subsystem 118. In other cases, there may be one ormore metabases associated with individual components, e.g., clientcomputing devices 102 and/or media agents 144. In some embodiments, adata classification database (metabase) may reside as one or more datastructures within management database 146, or may be otherwiseassociated with storage manager 140.

In some cases, the metabase(s) may be included in separate database(s)and/or on separate storage device(s) from primary data 112 and/orsecondary copies 116, such that operations related to the metabase donot significantly impact performance on other components in theinformation management system 100. In other cases, the metabase(s) maybe stored along with primary data 112 and/or secondary copies 116. Filesor other data objects can be associated with identifiers (e.g., tagentries, etc.) in the media agent 144 (or other indices) to facilitatesearches of stored data objects. Among a number of other benefits, themetabase can also allow efficient, automatic identification of files orother data objects to associate with secondary copy or other informationmanagement operations (e.g., in lieu of scanning an entire file system).Examples of compatible metabases and data classification operations areprovided in U.S. Pat. Nos. 8,229,954 and 7,747,579, which areincorporated by reference herein.

Encryption Operations

The information management system 100 in some cases is configured toprocess data (e.g., files or other data objects, secondary copies 116,etc.), according to an appropriate encryption algorithm (e.g., Blowfish,Advanced Encryption Standard [AES], Triple Data Encryption Standard[3-DES], etc.) to limit access and provide data security in theinformation management system 100. The information management system 100in some cases encrypts the data at the client level, such that theclient computing devices 102 (e.g., the data agents 142) encrypt thedata prior to forwarding the data to other components, e.g., beforesending the data to media agents 144 during a secondary copy operation.In such cases, the client computing device 102 may maintain or haveaccess to an encryption key or passphrase for decrypting the data uponrestore. Encryption can also occur when creating copies of secondarycopies, e.g., when creating auxiliary copies or archive copies. In yetfurther embodiments, the secondary storage devices 108 can implementbuilt-in, high performance hardware encryption.

Management and Reporting Operations

Certain embodiments leverage the integrated, ubiquitous nature of theinformation management system 100 to provide useful system-widemanagement and reporting functions. Examples of some compatiblemanagement and reporting techniques are provided in U.S. Pat. No.7,343,453, which is incorporated by reference herein.

Operations management can generally include monitoring and managing thehealth and performance of information management system 100 by, withoutlimitation, performing error tracking, generating granularstorage/performance metrics (e.g., job success/failure information,deduplication efficiency, etc.), generating storage modeling and costinginformation, and the like. As an example, a storage manager 140 or othercomponent in the information management system 100 may analyze trafficpatterns and suggest and/or automatically route data via a particularroute to minimize congestion. In some embodiments, the system cangenerate predictions relating to storage operations or storage operationinformation. Such predictions, which may be based on a trendinganalysis, may predict various network operations or resource usage, suchas network traffic levels, storage media use, use of bandwidth ofcommunication links, use of media agent components, etc. Furtherexamples of traffic analysis, trend analysis, prediction generation, andthe like are described in U.S. Pat. No. 7,343,453, which is incorporatedby reference herein.

In some configurations, a master storage manager 140 may track thestatus of storage operation cells in a hierarchy, such as the status ofjobs, system components, system resources, and other items, bycommunicating with storage managers 140 (or other components) in therespective storage operation cells. Moreover, the master storage manager140 may track the status of its associated storage operation cells andinformation management operations by receiving periodic status updatesfrom the storage managers 140 (or other components) in the respectivecells regarding jobs, system components, system resources, and otheritems. In some embodiments, a master storage manager 140 may storestatus information and other information regarding its associatedstorage operation cells and other system information in its index 150(or other location).

The master storage manager 140 or other component may also determinewhether certain storage-related criteria or other criteria aresatisfied, and perform an action or trigger event (e.g., data migration)in response to the criteria being satisfied, such as where a storagethreshold is met for a particular volume, or where inadequate protectionexists for certain data. For instance, in some embodiments, data fromone or more storage operation cells is used to dynamically andautomatically mitigate recognized risks, and/or to advise users of risksor suggest actions to mitigate these risks. For example, an informationmanagement policy may specify certain requirements (e.g., that a storagedevice should maintain a certain amount of free space, that secondarycopies should occur at a particular interval, that data should be agedand migrated to other storage after a particular period, that data on asecondary volume should always have a certain level of availability andbe restorable within a given time period, that data on a secondaryvolume may be mirrored or otherwise migrated to a specified number ofother volumes, etc.). If a risk condition or other criterion istriggered, the system may notify the user of these conditions and maysuggest (or automatically implement) an action to mitigate or otherwiseaddress the risk. For example, the system may indicate that data from aprimary copy 112 should be migrated to a secondary storage device 108 tofree space on the primary storage device 104. Examples of the use ofrisk factors and other triggering criteria are described in U.S. Pat.No. 7,343,453, which is incorporated by reference herein.

In some embodiments, the system 100 may also determine whether a metricor other indication satisfies particular storage criteria and, if so,perform an action. For example, as previously described, a storagepolicy or other definition might indicate that a storage manager 140should initiate a particular action if a storage metric or otherindication drops below or otherwise fails to satisfy specified criteriasuch as a threshold of data protection. Examples of such metrics aredescribed in U.S. Pat. No. 7,343,453, which is incorporated by referenceherein.

In some embodiments, risk factors may be quantified into certainmeasurable service or risk levels for ease of comprehension. Forexample, certain applications and associated data may be considered tobe more important by an enterprise than other data and services.Financial compliance data, for example, may be of greater importancethan marketing materials, etc. Network administrators may assignpriority values or “weights” to certain data and/or applications,corresponding to the relative importance. The level of compliance ofstorage operations specified for these applications may also be assigneda certain value. Thus, the health, impact, and overall importance of aservice may be determined, such as by measuring the compliance value andcalculating the product of the priority value and the compliance valueto determine the “service level” and comparing it to certain operationalthresholds to determine whether it is acceptable. Further examples ofthe service level determination are provided in U.S. Pat. No. 7,343,453,which is incorporated by reference herein.

The system 100 may additionally calculate data costing and dataavailability associated with information management operation cellsaccording to an embodiment of the invention. For instance, data receivedfrom the cell may be used in conjunction with hardware-relatedinformation and other information about system elements to determine thecost of storage and/or the availability of particular data in thesystem. Exemplary information generated could include how fast aparticular department is using up available storage space, how long datawould take to recover over a particular system pathway from a particularsecondary storage device, costs over time, etc. Moreover, in someembodiments, such information may be used to determine or predict theoverall cost associated with the storage of certain information. Thecost associated with hosting a certain application may be based, atleast in part, on the type of media on which the data resides, forexample. Storage devices may be assigned to a particular costcategories, for example. Further examples of costing techniques aredescribed in U.S. Pat. No. 7,343,453, which is incorporated by referenceherein.

Any of the above types of information (e.g., information related totrending, predictions, job, cell or component status, risk, servicelevel, costing, etc.) can generally be provided to users via the userinterface 158 in a single, integrated view or console (not shown). Theconsole may support a reporting capability that allows for thegeneration of a variety of reports, which may be tailored to aparticular aspect of information management. Report types may include:scheduling, event management, media management and data aging. Availablereports may also include backup history, data aging history, auxiliarycopy history, job history, library and drive, media in library, restorehistory, and storage policy, etc., without limitation. Such reports maybe specified and created at a certain point in time as a systemanalysis, forecasting, or provisioning tool. Integrated reports may alsobe generated that illustrate storage and performance metrics, risks andstorage costing information. Moreover, users may create their ownreports based on specific needs.

The integrated user interface 158 can include an option to show a“virtual view” of the system that graphically depicts the variouscomponents in the system using appropriate icons. As one example, theuser interface 158 may provide a graphical depiction of one or moreprimary storage devices 104, the secondary storage devices 108, dataagents 142 and/or media agents 144, and their relationship to oneanother in the information management system 100. The operationsmanagement functionality can facilitate planning and decision-making.For example, in some embodiments, a user may view the status of some orall jobs as well as the status of each component of the informationmanagement system 100. Users may then plan and make decisions based onthis data. For instance, a user may view high-level informationregarding storage operations for the information management system 100,such as job status, component status, resource status (e.g.,communication pathways, etc.), and other information. The user may alsodrill down or use other means to obtain more detailed informationregarding a particular component, job, or the like. Further examples ofsome reporting techniques and associated interfaces providing anintegrated view of an information management system are provided in U.S.Pat. No. 7,343,453, which is incorporated by reference herein.

The information management system 100 can also be configured to performsystem-wide e-discovery operations in some embodiments. In general,e-discovery operations provide a unified collection and searchcapability for data in the system, such as data stored in the secondarystorage devices 108 (e.g., backups, archives, or other secondary copies116). For example, the information management system 100 may constructand maintain a virtual repository for data stored in the informationmanagement system 100 that is integrated across source applications 110,different storage device types, etc. According to some embodiments,e-discovery utilizes other techniques described herein, such as dataclassification and/or content indexing.

Information Management Policies

As indicated previously, an information management policy 148 caninclude a data structure or other information source that specifies aset of parameters (e.g., criteria and rules) associated with secondarycopy and/or other information management operations.

One type of information management policy 148 is a storage policy.According to certain embodiments, a storage policy generally comprises adata structure or other information source that defines (or includesinformation sufficient to determine) a set of preferences or othercriteria for performing information management operations. Storagepolicies can include one or more of the following items: (1) what datawill be associated with the storage policy; (2) a destination to whichthe data will be stored; (3) datapath information specifying how thedata will be communicated to the destination; (4) the type of storageoperation to be performed; and (5) retention information specifying howlong the data will be retained at the destination (see, e.g., FIG. 1E).

As an illustrative example, data associated with a storage policy can belogically organized into groups. In some cases, these logical groupingscan be referred to as “sub-clients”. A sub-client may represent staticor dynamic associations of portions of a data volume. Sub-clients mayrepresent mutually exclusive portions. Thus, in certain embodiments, aportion of data may be given a label and the association is stored as astatic entity in an index, database or other storage location.Sub-clients may also be used as an effective administrative scheme oforganizing data according to data type, department within theenterprise, storage preferences, or the like. Depending on theconfiguration, sub-clients can correspond to files, folders, virtualmachines, databases, etc. In one exemplary scenario, an administratormay find it preferable to separate e-mail data from financial data usingtwo different sub-clients.

A storage policy can define where data is stored by specifying a targetor destination storage device (or group of storage devices). Forinstance, where the secondary storage device 108 includes a group ofdisk libraries, the storage policy may specify a particular disk libraryfor storing the sub-clients associated with the policy. As anotherexample, where the secondary storage devices 108 include one or moretape libraries, the storage policy may specify a particular tape libraryfor storing the sub-clients associated with the storage policy, and mayalso specify a drive pool and a tape pool defining a group of tapedrives and a group of tapes, respectively, for use in storing thesub-client data. While information in the storage policy can bestatically assigned in some cases, some or all of the information in thestorage policy can also be dynamically determined based on criteria,which can be set forth in the storage policy. For instance, based onsuch criteria, a particular destination storage device(s) (or otherparameter of the storage policy) may be determined based oncharacteristics associated with the data involved in a particularstorage operation, device availability (e.g., availability of asecondary storage device 108 or a media agent 144), network status andconditions (e.g., identified bottlenecks), user credentials, and thelike).

Datapath information can also be included in the storage policy. Forinstance, the storage policy may specify network pathways and componentsto utilize when moving the data to the destination storage device(s). Insome embodiments, the storage policy specifies one or more media agents144 for conveying data associated with the storage policy between thesource (e.g., one or more host client computing devices 102) anddestination (e.g., a particular target secondary storage device 108).

A storage policy can also specify the type(s) of operations associatedwith the storage policy, such as a backup, archive, snapshot, auxiliarycopy, or the like. Retention information can specify how long the datawill be kept, depending on organizational needs (e.g., a number of days,months, years, etc.)

Another type of information management policy 148 is a schedulingpolicy, which specifies when and how often to perform operations.Scheduling parameters may specify with what frequency (e.g., hourly,weekly, daily, event-based, etc.) or under what triggering conditionssecondary copy or other information management operations will takeplace. Scheduling policies in some cases are associated with particularcomponents, such as particular logical groupings of data associated witha storage policy (e.g., a sub-client), client computing device 102, andthe like. In one configuration, a separate scheduling policy ismaintained for particular logical groupings of data on a clientcomputing device 102. The scheduling policy specifies that those logicalgroupings are to be moved to secondary storage devices 108 every houraccording to storage policies associated with the respectivesub-clients.

When adding a new client computing device 102, administrators canmanually configure information management policies 148 and/or othersettings, e.g., via the user interface 158. However, this can be aninvolved process resulting in delays, and it may be desirable to begindata protection operations quickly, without awaiting human intervention.Thus, in some embodiments, the information management system 100automatically applies a default configuration to client computing device102. As one example, when one or more data agent(s) 142 are installed onone or more client computing devices 102, the installation script mayregister the client computing device 102 with the storage manager 140,which in turn applies the default configuration to the new clientcomputing device 102. In this manner, data protection operations canbegin substantially immediately. The default configuration can include adefault storage policy, for example, and can specify any appropriateinformation sufficient to begin data protection operations. This caninclude a type of data protection operation, scheduling information, atarget secondary storage device 108, data path information (e.g., aparticular media agent 144), and the like.

Other types of information management policies 148 are possible,including one or more audit (or security) policies. An audit policy is aset of preferences, rules and/or criteria that protect sensitive data inthe information management system 100. For example, an audit policy maydefine “sensitive objects” as files or objects that contain particularkeywords (e.g., “confidential,” or “privileged”) and/or are associatedwith particular keywords (e.g., in metadata) or particular flags (e.g.,in metadata identifying a document or email as personal, confidential,etc.). An audit policy may further specify rules for handling sensitiveobjects. As an example, an audit policy may require that a reviewerapprove the transfer of any sensitive objects to a cloud storage site,and that if approval is denied for a particular sensitive object, thesensitive object should be transferred to a local primary storage device104 instead. To facilitate this approval, the audit policy may furtherspecify how a secondary storage computing device 106 or other systemcomponent should notify a reviewer that a sensitive object is slated fortransfer.

Another type of information management policy 148 is a provisioningpolicy. A provisioning policy can include a set of preferences,priorities, rules, and/or criteria that specify how client computingdevices 102 (or groups thereof) may utilize system resources, such asavailable storage on cloud storage and/or network bandwidth. Aprovisioning policy specifies, for example, data quotas for particularclient computing devices 102 (e.g., a number of gigabytes that can bestored monthly, quarterly or annually). The storage manager 140 or othercomponents may enforce the provisioning policy. For instance, the mediaagents 144 may enforce the policy when transferring data to secondarystorage devices 108. If a client computing device 102 exceeds a quota, abudget for the client computing device 102 (or associated department) isadjusted accordingly or an alert may trigger.

While the above types of information management policies 148 have beendescribed as separate policies, one or more of these can be generallycombined into a single information management policy 148. For instance,a storage policy may also include or otherwise be associated with one ormore scheduling, audit, or provisioning policies or operationalparameters thereof. Moreover, while storage policies are typicallyassociated with moving and storing data, other policies may beassociated with other types of information management operations. Thefollowing is a non-exhaustive list of items the information managementpolicies 148 may specify:

-   -   schedules or other timing information, e.g., specifying when        and/or how often to perform information management operations;    -   the type of copy 116 (e.g., type of secondary copy) and/or copy        format (e.g., snapshot, backup, archive, HSM, etc.);    -   a location or a class or quality of storage for storing        secondary copies 116 (e.g., one or more particular secondary        storage devices 108);    -   preferences regarding whether and how to encrypt, compress,        deduplicate, or otherwise modify or transform secondary copies        116;    -   which system components and/or network pathways (e.g., preferred        media agents 144) should be used to perform secondary storage        operations;    -   resource allocation among different computing devices or other        system components used in performing information management        operations (e.g., bandwidth allocation, available storage        capacity, etc.);    -   whether and how to synchronize or otherwise distribute files or        other data objects across multiple computing devices or hosted        services; and    -   retention information specifying the length of time primary data        112 and/or secondary copies 116 should be retained, e.g., in a        particular class or tier of storage devices, or within the        information management system 100.

Policies can additionally specify or depend on a variety of historicalor current criteria that may be used to determine which rules to applyto a particular data object, system component, or information managementoperation, such as:

-   -   frequency with which primary data 112 or a secondary copy 116 of        a data object or metadata has been or is predicted to be used,        accessed, or modified;    -   time-related factors (e.g., aging information such as time since        the creation or modification of a data object);    -   deduplication information (e.g., hashes, data blocks,        deduplication block size, deduplication efficiency or other        metrics);    -   an estimated or historic usage or cost associated with different        components (e.g., with secondary storage devices 108);    -   the identity of users, applications 110, client computing        devices 102 and/or other computing devices that created,        accessed, modified, or otherwise utilized primary data 112 or        secondary copies 116;    -   a relative sensitivity (e.g., confidentiality, importance) of a        data object, e.g., as determined by its content and/or metadata;    -   the current or historical storage capacity of various storage        devices;    -   the current or historical network capacity of network pathways        connecting various components within the storage operation cell;    -   access control lists or other security information; and    -   the content of a particular data object (e.g., its textual        content) or of metadata associated with the data object.        Exemplary Storage Policy and Secondary Storage Operations

FIG. 1E includes a data flow diagram depicting performance of storageoperations by an embodiment of an information management system 100,according to an exemplary storage policy 148A. The informationmanagement system 100 includes a storage manger 140, a client computingdevice 102 having a file system data agent 142A and an email data agent142B operating thereon, a primary storage device 104, two media agents144A, 144B, and two secondary storage devices 108A, 108B: a disk library108A and a tape library 108B. As shown, the primary storage device 104includes primary data 112A, which is associated with a logical groupingof data associated with a file system, and primary data 1128, which isassociated with a logical grouping of data associated with email.Although for simplicity the logical grouping of data associated with thefile system is referred to as a file system sub-client, and the logicalgrouping of data associated with the email is referred to as an emailsub-client, the techniques described with respect to FIG. 1E can beutilized in conjunction with data that is organized in a variety ofother manners.

As indicated by the dashed box, the second media agent 144B and the tapelibrary 108B are “off-site”, and may therefore be remotely located fromthe other components in the information management system 100 (e.g., ina different city, office building, etc.). Indeed, “off-site” may referto a magnetic tape located in storage, which must be manually retrievedand loaded into a tape drive to be read. In this manner, informationstored on the tape library 108B may provide protection in the event of adisaster or other failure.

The file system sub-client and its associated primary data 112A incertain embodiments generally comprise information generated by the filesystem and/or operating system of the client computing device 102, andcan include, for example, file system data (e.g., regular files, filetables, mount points, etc.), operating system data (e.g., registries,event logs, etc.), and the like. The e-mail sub-client, on the otherhand, and its associated primary data 1128, include data generated by ane-mail application operating on the client computing device 102, and caninclude mailbox information, folder information, emails, attachments,associated database information, and the like. As described above, thesub-clients can be logical containers, and the data included in thecorresponding primary data 112A, 112B may or may not be storedcontiguously.

The exemplary storage policy 148A includes backup copy preferences (orrule set) 160, disaster recovery copy preferences rule set 162, andcompliance copy preferences or rule set 164. The backup copy rule set160 specifies that it is associated with a file system sub-client 166and an email sub-client 168. Each of these sub-clients 166, 168 areassociated with the particular client computing device 102. The backupcopy rule set 160 further specifies that the backup operation will bewritten to the disk library 108A, and designates a particular mediaagent 144A to convey the data to the disk library 108A. Finally, thebackup copy rule set 160 specifies that backup copies created accordingto the rule set 160 are scheduled to be generated on an hourly basis andto be retained for 30 days. In some other embodiments, schedulinginformation is not included in the storage policy 148A, and is insteadspecified by a separate scheduling policy.

The disaster recovery copy rule set 162 is associated with the same twosub-clients 166, 168. However, the disaster recovery copy rule set 162is associated with the tape library 108B, unlike the backup copy ruleset 160. Moreover, the disaster recovery copy rule set 162 specifiesthat a different media agent, namely 144B, will be used to convey thedata to the tape library 108B. As indicated, disaster recovery copiescreated according to the rule set 162 will be retained for 60 days, andwill be generated on a daily basis. Disaster recovery copies generatedaccording to the disaster recovery copy rule set 162 can provideprotection in the event of a disaster or other catastrophic data lossthat would affect the backup copy 116A maintained on the disk library108A.

The compliance copy rule set 164 is only associated with the emailsub-client 168, and not the file system sub-client 166. Compliancecopies generated according to the compliance copy rule set 164 willtherefore not include primary data 112A from the file system sub-client166. For instance, the organization may be under an obligation to storeand maintain copies of email data for a particular period of time (e.g.,10 years) to comply with state or federal regulations, while similarregulations do not apply to the file system data. The compliance copyrule set 164 is associated with the same tape library 108B and mediaagent 144B as the disaster recovery copy rule set 162, although adifferent storage device or media agent could be used in otherembodiments. Finally, the compliance copy rule set 164 specifies thatcopies generated under the compliance copy rule set 164 will be retainedfor 10 years, and will be generated on a quarterly basis.

At step 1, the storage manager 140 initiates a backup operationaccording to the backup copy rule set 160. For instance, a schedulingservice running on the storage manager 140 accesses schedulinginformation from the backup copy rule set 160 or a separate schedulingpolicy associated with the client computing device 102, and initiates abackup copy operation on an hourly basis. Thus, at the scheduled timeslot the storage manager 140 sends instructions to the client computingdevice 102 (i.e., to both data agent 142A and data agent 142B) to beginthe backup operation.

At step 2, the file system data agent 142A and the email data agent 142Boperating on the client computing device 102 respond to the instructionsreceived from the storage manager 140 by accessing and processing theprimary data 112A, 112B involved in the copy operation, which can befound in primary storage device 104. Because the operation is a backupcopy operation, the data agent(s) 142A, 142B may format the data into abackup format or otherwise process the data.

At step 3, the client computing device 102 communicates the retrieved,processed data to the first media agent 144A, as directed by the storagemanager 140, according to the backup copy rule set 160. In some otherembodiments, the information management system 100 may implement aload-balancing, availability-based, or other appropriate algorithm toselect from the available set of media agents 144A, 144B. Regardless ofthe manner the media agent 144A is selected, the storage manager 140 mayfurther keep a record in the storage manager database 146 of theassociation between the selected media agent 144A and the clientcomputing device 102 and/or between the selected media agent 144A andthe backup copy 116A.

The target media agent 144A receives the data from the client computingdevice 102, and at step 4 conveys the data to the disk library 108A tocreate the backup copy 116A, again at the direction of the storagemanager 140 and according to the backup copy rule set 160. The secondarystorage device 108A can be selected in other ways. For instance, themedia agent 144A may have a dedicated association with a particularsecondary storage device(s), or the storage manager 140 or media agent144A may select from a plurality of secondary storage devices, e.g.,according to availability, using one of the techniques described in U.S.Pat. No. 7,246,207, which is incorporated by reference herein.

The media agent 144A can also update its index 153 to include dataand/or metadata related to the backup copy 116A, such as informationindicating where the backup copy 116A resides on the disk library 108A,data and metadata for cache retrieval, etc. The storage manager 140 maysimilarly update its index 150 to include information relating to thestorage operation, such as information relating to the type of storageoperation, a physical location associated with one or more copiescreated by the storage operation, the time the storage operation wasperformed, status information relating to the storage operation, thecomponents involved in the storage operation, and the like. In somecases, the storage manager 140 may update its index 150 to include someor all of the information stored in the index 153 of the media agent144A. After the 30 day retention period expires, the storage manager 140instructs the media agent 144A to delete the backup copy 116A from thedisk library 108A. Indexes 150 and/or 153 are updated accordingly.

At step 5, the storage manager 140 initiates the creation of a disasterrecovery copy 1168 according to the disaster recovery copy rule set 162.

At step 6, illustratively based on the instructions received from thestorage manager 140 at step 5, the specified media agent 144B retrievesthe most recent backup copy 116A from the disk library 108A.

At step 7, again at the direction of the storage manager 140 and asspecified in the disaster recovery copy rule set 162, the media agent144B uses the retrieved data to create a disaster recovery copy 1168 onthe tape library 108B. In some cases, the disaster recovery copy 1168 isa direct, mirror copy of the backup copy 116A, and remains in the backupformat. In other embodiments, the disaster recovery copy 1168 may begenerated in some other manner, such as by using the primary data 112A,112B from the primary storage device 104 as source data. The disasterrecovery copy operation is initiated once a day and the disasterrecovery copies 1168 are deleted after 60 days; indexes are updatedaccordingly when/after each information management operation isexecuted/completed.

At step 8, the storage manager 140 initiates the creation of acompliance copy 116C, according to the compliance copy rule set 164. Forinstance, the storage manager 140 instructs the media agent 144B tocreate the compliance copy 116C on the tape library 108B at step 9, asspecified in the compliance copy rule set 164. In the example, thecompliance copy 116C is generated using the disaster recovery copy 1168.In other embodiments, the compliance copy 116C is instead generatedusing either the primary data 1128 corresponding to the email sub-clientor using the backup copy 116A from the disk library 108A as source data.As specified, in the illustrated example, compliance copies 116C arecreated quarterly, and are deleted after ten years, and indexes are keptup-to-date accordingly.

While not shown in FIG. 1E, at some later point in time, a restoreoperation can be initiated involving one or more of the secondary copies116A, 1168, 116C. As one example, a user may manually initiate a restoreof the backup copy 116A by interacting with the user interface 158 ofthe storage manager 140. The storage manager 140 then accesses data inits index 150 (and/or the respective storage policy 148A) associatedwith the selected backup copy 116A to identify the appropriate mediaagent 144A and/or secondary storage device 108A.

In other cases, a media agent may be selected for use in the restoreoperation based on a load balancing algorithm, an availability basedalgorithm, or other criteria. The selected media agent 144A retrievesthe data from the disk library 108A. For instance, the media agent 144Amay access its index 153 to identify a location of the backup copy 116Aon the disk library 108A, or may access location information residing onthe disk 108A itself.

When the backup copy 116A was recently created or accessed, the mediaagent 144A accesses a cached version of the backup copy 116A residing inthe index 153, without having to access the disk library 108A for someor all of the data. Once it has retrieved the backup copy 116A, themedia agent 144A communicates the data to the source client computingdevice 102. Upon receipt, the file system data agent 142A and the emaildata agent 142B may unpackage (e.g., restore from a backup format to thenative application format) the data in the backup copy 116A and restorethe unpackaged data to the primary storage device 104.

Exemplary Applications of Storage Policies

The storage manager 140 may permit a user to specify aspects of thestorage policy 148A. For example, the storage policy can be modified toinclude information governance policies to define how data should bemanaged in order to comply with a certain regulation or businessobjective. The various policies may be stored, for example, in themanagement database 146. An information governance policy may comprise aclassification policy, which is described herein. An informationgovernance policy may align with one or more compliance tasks that areimposed by regulations or business requirements. Examples of informationgovernance policies might include a Sarbanes-Oxley policy, a HIPAApolicy, an electronic discovery (E-Discovery) policy, and so on.

Information governance policies allow administrators to obtain differentperspectives on all of an organization's online and offline data,without the need for a dedicated data silo created solely for eachdifferent viewpoint. As described previously, the data storage systemsherein build a centralized index that reflects the contents of adistributed data set that spans numerous clients and storage devices,including both primary and secondary copies, and online and offlinecopies. An organization may apply multiple information governancepolicies in a top-down manner over that unified data set and indexingschema in order to permit an organization to view and manipulate thesingle data set through different lenses, each of which is adapted to aparticular compliance or business goal. Thus, for example, by applyingan E-discovery policy and a Sarbanes-Oxley policy, two different groupsof users in an organization can conduct two very different analyses ofthe same underlying physical set of data copies, which may bedistributed throughout the organization and information managementsystem.

A classification policy defines a taxonomy of classification terms ortags relevant to a compliance task and/or business objective. Aclassification policy may also associate a defined tag with aclassification rule. A classification rule defines a particularcombination of criteria, such as users who have created, accessed ormodified a document or data object; file or application types; contentor metadata keywords; clients or storage locations; dates of datacreation and/or access; review status or other status within a workflow(e.g., reviewed or un-reviewed); modification times or types ofmodifications; and/or any other data attributes in any combination,without limitation. A classification rule may also be defined usingother classification tags in the taxonomy. The various criteria used todefine a classification rule may be combined in any suitable fashion,for example, via Boolean operators, to define a complex classificationrule. As an example, an E-discovery classification policy might define aclassification tag “privileged” that is associated with documents ordata objects that (1) were created or modified by legal departmentstaff, or (2) were sent to or received from outside counsel via email,or (3) contain one of the following keywords: “privileged” or “attorney”or “counsel”, or other like terms.

One specific type of classification tag, which may be added to an indexat the time of indexing, is an entity tag. An entity tag may be, forexample, any content that matches a defined data mask format. Examplesof entity tags might include, e.g., social security numbers (e.g., anynumerical content matching the formatting mask XXX-XX-XXXX), credit cardnumbers (e.g., content having a 13-16 digit string of numbers), SKUnumbers, product numbers, etc.

A user may define a classification policy by indicating criteria,parameters or descriptors of the policy via a graphical user interface,such as a form or page with fields to be filled in, pull-down menus orentries allowing one or more of several options to be selected, buttons,sliders, hypertext links or other known user interface tools forreceiving user input, etc. For example, a user may define certain entitytags, such as a particular product number or project ID code that isrelevant in the organization. In some implementations, theclassification policy can be implemented using cloud-based techniques.For example, the storage devices may be cloud storage devices, and thestorage manager 140 may execute cloud service provider API over anetwork to classify data stored on cloud storage devices.

Exemplary Secondary Copy Formatting

The formatting and structure of secondary copies 116 can vary, dependingon the embodiment. In some cases, secondary copies 116 are formatted asa series of logical data units or “chunks” (e.g., 512 MB, 1 GB, 2 GB, 4GB, or 8 GB chunks). This can facilitate efficient communication andwriting to secondary storage devices 108, e.g., according to resourceavailability. For example, a single secondary copy 116 may be written ona chunk-by-chunk basis to a single secondary storage device 108 oracross multiple secondary storage devices 108. In some cases, users canselect different chunk sizes, e.g., to improve throughput to tapestorage devices.

Generally, each chunk can include a header and a payload. The payloadcan include files (or other data units) or subsets thereof included inthe chunk, whereas the chunk header generally includes metadata relatingto the chunk, some or all of which may be derived from the payload. Forexample, during a secondary copy operation, the media agent 144, storagemanager 140, or other component may divide the associated files intochunks and generate headers for each chunk by processing the constituentfiles. The headers can include a variety of information such as fileidentifier(s), volume(s), offset(s), or other information associatedwith the payload data items, a chunk sequence number, etc. Importantly,in addition to being stored with the secondary copy 116 on the secondarystorage device 108, the chunk headers can also be stored to the index153 of the associated media agent(s) 144 and/or the index 150. This isuseful in some cases for providing faster processing of secondary copies116 during restores or other operations. In some cases, once a chunk issuccessfully transferred to a secondary storage device 108, thesecondary storage device 108 returns an indication of receipt, e.g., tothe media agent 144 and/or storage manager 140, which may update theirrespective indexes 153, 150 accordingly. During restore, chunks may beprocessed (e.g., by the media agent 144) according to the information inthe chunk header to reassemble the files.

Data can also be communicated within the information management system100 in data channels that connect the client computing devices 102 tothe secondary storage devices 108. These data channels can be referredto as “data streams”, and multiple data streams can be employed toparallelize an information management operation, improving data transferrate, among providing other advantages. Example data formattingtechniques including techniques involving data streaming, chunking, andthe use of other data structures in creating copies (e.g., secondarycopies) are described in U.S. Pat. Nos. 7,315,923 and 8,156,086, and8,578,120, each of which is incorporated by reference herein.

FIGS. 1F and 1G are diagrams of example data streams 170 and 171,respectively, which may be employed for performing data storageoperations. Referring to FIG. 1F, the data agent 142 forms the datastream 170 from the data associated with a client computing device 102(e.g., primary data 112). The data stream 170 is composed of multiplepairs of stream header 172 and stream data (or stream payload) 174. Thedata streams 170 and 171 shown in the illustrated example are for asingle-instanced storage operation, and a stream payload 174 thereforemay include both single-instance (“SI”) data and/or non-SI data. Astream header 172 includes metadata about the stream payload 174. Thismetadata may include, for example, a length of the stream payload 174,an indication of whether the stream payload 174 is encrypted, anindication of whether the stream payload 174 is compressed, an archivefile identifier (ID), an indication of whether the stream payload 174 issingle instanceable, and an indication of whether the stream payload 174is a start of a block of data.

Referring to FIG. 1G, the data stream 171 has the stream header 172 andstream payload 174 aligned into multiple data blocks. In this example,the data blocks are of size 64 KB. The first two stream header 172 andstream payload 174 pairs comprise a first data block of size 64 KB. Thefirst stream header 172 indicates that the length of the succeedingstream payload 174 is 63 KB and that it is the start of a data block.The next stream header 172 indicates that the succeeding stream payload174 has a length of 1 KB and that it is not the start of a new datablock. Immediately following stream payload 174 is a pair comprising anidentifier header 176 and identifier data 178. The identifier header 176includes an indication that the succeeding identifier data 178 includesthe identifier for the immediately previous data block. The identifierdata 178 includes the identifier that the data agent 142 generated forthe data block. The data stream 171 also includes other stream header172 and stream payload 174 pairs, which may be for SI data and/or fornon-SI data.

FIG. 1H is a diagram illustrating the data structures 180 that may beused to store blocks of SI data and non-SI data on the storage device(e.g., secondary storage device 108). According to certain embodiments,the data structures 180 do not form part of a native file system of thestorage device. The data structures 180 include one or more volumefolders 182, one or more chunk folders 184/185 within the volume folder182, and multiple files within the chunk folder 184. Each chunk folder184/185 includes a metadata file 186/187, a metadata index file 188/189,one or more container files 190/191/193, and a container index file192/194. The metadata file 186/187 stores non-SI data blocks as well aslinks to SI data blocks stored in container files. The metadata indexfile 188/189 stores an index to the data in the metadata file 186/187.The container files 190/191/193 store SI data blocks. The containerindex file 192/194 stores an index to the container files 190/191/193.Among other things, the container index file 192/194 stores anindication of whether a corresponding block in a container file190/191/193 is referred to by a link in a metadata file 186/187. Forexample, data block B2 in the container file 190 is referred to by alink in the metadata file 187 in the chunk folder 185. Accordingly, thecorresponding index entry in the container index file 192 indicates thatthe data block B2 in the container file 190 is referred to. As anotherexample, data block B1 in the container file 191 is referred to by alink in the metadata file 187, and so the corresponding index entry inthe container index file 192 indicates that this data block is referredto.

As an example, the data structures 180 illustrated in FIG. 1H may havebeen created as a result of two storage operations involving two clientcomputing devices 102. For example, a first storage operation on a firstclient computing device 102 could result in the creation of the firstchunk folder 184, and a second storage operation on a second clientcomputing device 102 could result in the creation of the second chunkfolder 185. The container files 190/191 in the first chunk folder 184would contain the blocks of SI data of the first client computing device102. If the two client computing devices 102 have substantially similardata, the second storage operation on the data of the second clientcomputing device 102 would result in the media agent 144 storingprimarily links to the data blocks of the first client computing device102 that are already stored in the container files 190/191. Accordingly,while a first storage operation may result in storing nearly all of thedata subject to the storage operation, subsequent storage operationsinvolving similar data may result in substantial data storage spacesavings, because links to already stored data blocks can be storedinstead of additional instances of data blocks.

If the operating system of the secondary storage computing device 106 onwhich the media agent 144 operates supports sparse files, then when themedia agent 144 creates container files 190/191/193, it can create themas sparse files. A sparse file is type of file that may include emptyspace (e.g., a sparse file may have real data within it, such as at thebeginning of the file and/or at the end of the file, but may also haveempty space in it that is not storing actual data, such as a contiguousrange of bytes all having a value of zero). Having the container files190/191/193 be sparse files allows the media agent 144 to free up spacein the container files 190/191/193 when blocks of data in the containerfiles 190/191/193 no longer need to be stored on the storage devices. Insome examples, the media agent 144 creates a new container file190/191/193 when a container file 190/191/193 either includes 100 blocksof data or when the size of the container file 190 exceeds 50 MB. Inother examples, the media agent 144 creates a new container file190/191/193 when a container file 190/191/193 satisfies other criteria(e.g., it contains from approximately 100 to approximately 1000 blocksor when its size exceeds approximately 50 MB to 1 GB).

In some cases, a file on which a storage operation is performed maycomprise a large number of data blocks. For example, a 100 MB file maycomprise 400 data blocks of size 256 KB. If such a file is to be stored,its data blocks may span more than one container file, or even more thanone chunk folder. As another example, a database file of 20 GB maycomprise over 40,000 data blocks of size 512 KB. If such a database fileis to be stored, its data blocks will likely span multiple containerfiles, multiple chunk folders, and potentially multiple volume folders.Restoring such files may require accessing multiple container files,chunk folders, and/or volume folders to obtain the requisite datablocks.

Example Hybrid Drive Caching System

Detailed example embodiments of an intelligent hybrid drive cachingsystem will now be described with respect to the FIGURES. FIG. 2 depictsan example computing system 200 that can implement intelligent cachingusing a hybrid drive. The computing system 200 includes a computingdevice 210 in communication with a storage system 230. For example, thecomputing device 210 may be an example of one of the client computingdevices described above with respect to FIGS. 1A-1H. Alternatively, thecomputing device 210 may be a server. The computing device 210 includesone or more processors 212 and a memory 214. The memory 214 may be avolatile memory, such as random access memory (RAM) or the like.Although the memory 214 may include one or more memory devices, a singlememory 214 structure is shown for convenience. The memory 214 includesone or more applications 216, an operating system 218, a file systemmount point 220, and a storage driver 222. The file system mount point220 can be an interface for the one or more applications 216 and/or theoperating system 218 to read and write to a file system in the storagesystem 230. Although not shown, an interface may also be included in thememory 214 for communicating with a database that may be included in thestorage system 230.

The storage driver 222 may include one or more modules or componentsthat execute in the one or more processors 212 and that can implementany of the features or processes described herein. The storage driver222 can receive input/output (I/O) requests, such as read and writerequests, and can communicate these read and write requests to thestorage system 230. The storage driver 222 may advantageously implementthe intelligent caching features described herein so as to process theread and/or write requests in an efficient manner and thereby improvecomputing performance or usage of computing resources. In oneembodiment, the storage driver 222 is part of the data agent 142 (seee.g., FIG. 1C) and may perform at least some backup operations includingfull backups, incremental backups, differential backups, snapshotoperations, or the like. Although the storage driver 222 is shownimplemented in the computing device 210, at least some of thefunctionality of the storage driver 222 may instead be implementeddirectly in the storage system 230.

In the depicted embodiment, the storage system 230 includes an interface232 that communicates with the storage driver 222. The interface 232 mayinclude one or more functions, routines, or an application programminginterface (API) that the storage driver 222 can use to access read andwrite (or other) functionality of the storage system 230. The interface232 is shown in communication with a hybrid drive controller 234. Thehybrid drive controller 234 can include one or more processors ormicrocontrollers that send read, write, erase, and other commands to ahard disk 236 and/or solid state drive 238. The hybrid drive controller234 can communicate with the hard disk 236 and the SSD 238 over a bus237 in some embodiments.

The hard disk 236 may be any currently-available hard disk drive. A harddisk drive typically includes one or more spinning platters upon whichis coated a magnetic film that can store data. A moving armature in thehard disk drive can access data encoded magnetically on the spinningplatters and can read this data and/or write new data. In contrast, theSSD 238 may include flash memory or the like together with one or moremicrocontrollers and associated logic that can store data persistentlyin the flash memory. Because flash memory can be much faster to read andwrite to than a spinning disk, the SSD 238 may be able to perform readsand writes much faster than the hard disk 236.

In some embodiments, the configuration of the storage system 230 shown,with both a hard disk 236 and an SSD 238, may be referred to as a hybriddrive or hybrid disk. As a hybrid drive, the hard disk 236 and the SSD238 may be separate devices (as shown) or alternatively may be in asingle device. The hybrid drive may also be a solid state hybrid drive(SSHD), particularly so if the hard disk 236 and the SSD 238 arecombined in a single device. The term “hybrid drive” may also have itsordinary meaning herein.

The SSD 238 may be used as a cache for the hard disk 236. The SSD 238can cache certain I/O so that frequently accessed data stored in thehard disk 236 can be accessed more quickly from the SSD 238. One reasonfor using an SSD 238 as a cache instead of replacing the hard disk 236with SSD technology entirely is that flash memory can be expensiverelative to hard disk technology. Thus, the storage system 230 canprovide a compromise of price versus storage capacity by including ahard disk 236 with large storage capacity and an SSD 238 cache that isfaster yet has smaller storage capacity than the hard disk 236.

Although the storage system 230 includes a single hard disk 236 and asingle solid state drive 238, multiple hard disks 236 or multiple SSDs238 may be included in other embodiments. Such devices may be in a RAIDconfiguration or as part of a networked storage system, such as a NAS orNFS system or the like. The storage system 230 is an example of theprimary storage devices described above with respect to FIGS. 1A-1H,which can store primary data. However the storage system 230 may also beused as the secondary storage devices of FIGS. 1A-1H in someembodiments.

Advantageously, in certain embodiments the storage driver 222 canimplement one or more caching algorithms that can efficiently use thefeatures of the SSD 238. Such intelligent cache algorithms can improvestorage utilization and I/O efficiency by taking into account thewrite-wearing limitations of the SSD 238 described above. Accordingly,the storage driver 222 can cache to the SSD 238 while avoiding writingtoo frequently to the SSD 228, to increase or attempt to increase thelifespan of the SSD 238. The algorithms implemented by the storagedriver 222 can also to improve caching performance in some embodiments.The storage driver 222 may, for instance, write data to the SSD 228 oncethat data has been read from the hard disk 236 or memory multiple timesto avoid or attempt to avoid writing data that has been read only once.The storage driver 222 may also write large chunks of data to the SSD228 at once instead of a single unit of data at a time. Further, thestorage driver 222 can write to the SSD 228 in a circular fashion,overwriting (for example) the oldest or least-recently used data toavoid or attempt to avoid overwriting the same area of the SSD multipletimes in a row.

One example of a caching algorithm that may be implemented by thestorage driver 222 is shown in FIG. 3, namely, an example hybrid drivecaching process 300. The hybrid drive caching process 300 can beimplemented by the storage driver 222 or by other hardware or softwarethat can perform these features. In certain embodiments, the hybriddrive caching process 300 caches read operations performed on the harddisk 236 while not caching write operations performed on the hard disk236. An example process for handling writes is described in furtherdetail below with respect to FIG. 8. In other embodiments, writes mayalso be cached.

At block 302, the storage driver 222 receives page read requests. Pageread requests may be received from the file system mount point 220 bythe storage driver 222 or from an equivalent database management systemor the like. The read requests may be for data elements, referred toherein as “pages” which (in addition to having their ordinary meaning)can be the smallest unit of data for performing memory allocations inthe storage system 330. An example size of a page in some systems is 4kilobytes (KB), although other systems may use different page sizes. Inother systems, the smallest unit of data for performing memoryallocations is called a block. For convenience, this specificationprimarily uses the term “page” to refer to either a page or block. Itshould be noted, however, that in an SSD, a “block” can also refer to aplurality of pages, and sometimes this specification refers to “blocks”in that context.

At block 304, pages are initially read by the storage driver 222 fromthe hard disk 236. In one embodiment, pages are not cached by thestorage driver 222 to the SSD 238 when only read once because such pagesmay not be read again for a long time, if ever. Accordingly, the storagedriver 222 may wait until a page has been read at least twice beforecaching. In other embodiments, the storage driver 222 caches pages uponbeing read just once.

At block 306, the storage driver 222 receives additional page readrequests for pages that have already been read from the hard disk 236.These additional read requests can signify that these pages are eligiblefor caching or that they are good candidates for caching. In otherembodiments, the storage driver 222 waits until a page has been readmore than two times, such as three times or more, before indicating thatsuch pages may be eligible for caching.

At block 308, the storage driver 222 initially caches the pages inmemory 214 in response to the additional read requests. This step isoptional and may be omitted in some embodiments. Caching pages in memory214 can include more than merely loading the page in memory 214, butrather, loading the page or pages in a memory cache that is some subsetof the full size or capacity of the memory 214. Pages can first becached in memory so that the pages can be read quickly from the memory.Subsequently, pages can be cached to the SSD and read from the SSD 238instead of from memory.

Caching read data in memory with or in the storage driver 222 isoptional, and is aimed primarily at SSDs which may not have a filesystem built on top of them or include a file system, and which may bereferred to as “raw SSDs”. For instance, when the second read for thesame page is received (and the storage driver 222 can use the secondread as an indication that the data should be cached on SSD), thestorage driver 222 will not have to re-read the data from the HDD.Instead, the storage driver 222 can access the data in the memory cache.If there is a file system built on top of the SSD, then the file systemwill likely use an in-memory per-file cache included in the SSD. Thatcache may be more extensive than a separate memory cache that thestorage driver 222 can provide, so it may be undesirable to double-cachethe data in a separate memory cache provided by the storage driver 222.However, the storage driver 222 can still use the separate in-memorycache to streamline the process of SSD block relocation.

It can be advantageous in some embodiments to cache multiple pages tothe SSD 238 at once because writing a single page to the SSD 238 at atime can be expensive in terms of computing resources and write wear onthe SSD 238. This can be due to the unique characteristics of the SSD238, which initially may have to erase an entire block of pages beforewriting a new page to that block. Accordingly, if a single page is to bewritten and a block of pages has to be erased before such page iswritten, this operation can be time consuming and unduly write-wearingon the SSD 238.

To avoid or attempt to avoid this problem, at block 310, the storagedriver 222 accumulates references or pointers to a set of pages thathave been requested to be read multiple times. These references orpointers can be stored in a buffer or other data structure. Suchaccumulation can thereby store or create an indication that these pagesare to be cached without actually caching them yet. Accumulating anumber of pages or references to those pages that are to be written tothe SSD 238 and then writing such pages at once (block 312) can moreefficiently wear the SSD 238 and more efficiently write to the SSD 238in a way that may be faster and improve caching performance.

Writing to the SSD 238 can also be performed in an efficient way by (atblock 312) writing the set of pages to the SSD 238 in a circular fashionwhile pruning older SSD 238 entries. Writing to the SSD 238 circularlycan be performed by the storage driver 222 overwriting (for example)oldest entries or least-used entries according to a caching algorithm.In contrast, if the storage driver 222 wrote to the SSD 238 randomly,the storage driver 222 might overwrite some cells too many times,causing the SSD 238 to fail prematurely.

Example operations of the process 300 are described in greater detailbelow with respect to the remaining FIGURES.

Turning to FIG. 4, an example set of data structures 400 is shown. Thedata structures 400 may be created and/or maintained by the storagedriver 222 and may be stored in the memory 214. The data structures 400may also be saved to either the hard disk 236 or the SSD 238. Four maindata structures 400 are shown. These include a hash table 410, an LRUlist 430, an outgoing SSD buffer 450 and a back pointer array 470. Thesedata structures, or some subset thereof, can enable the storage driver222 to intelligently manage caching of the SSD 238. For instance, one ormore of the data structures shown can be used by the storage driver 222to accumulate references to a set of pages that have been requestedmultiple times and to write pages to the SSD 238 in a circular fashionwhile pruning older SSD entries as described above with respect to FIG.3.

The hash table 410 can include functionality for mapping pages tostorage locations whether in the memory 214, on the hard disk 236, or onthe SSD 238. When a page number is read, the storage driver 222 cancreate or populate an entry 412 in the hash table 410 corresponding tothat page number and can store a reference or pointer related to thatpage in the entry 412 of the hash table 410. The hash table 410 can bekeyed or indexed by page numbers, or if multiple devices are used (suchas multiple hard disks or SSDs), by both the device identifier (ID) andpage number. The storage driver 222 may, for instance, compute a hashfunction of the device ID and page number (or simply page number) tocreate or identify a location or index in the hash table 410. Thus, witha device ID and/or page number, the storage driver 222 can quicklycreate or look up an entry 412 in the hash table 410 that corresponds tothe relevant device ID and/or page number.

Upon the first read or first hit of a page, the storage driver 222 cancreate a first node 420 that includes a location pointer in the hashtable 410 entry for that page. The “first hit” can refer to there beingno element corresponding to this page in the hash table 410. It may bethe first hit after a reboot of the system 200, or it may be an attemptto access a page that hasn't been read for an extended period of time(so that other reads have already pushed the corresponding element fromthe hash). This hash table 410 can be reviewed both to remember orotherwise determine where a particular page is stored on the SSD and asa place to accumulate page access statistics. When an existing hashelement is hit for the second time, the storage driver 222 can use thissecond hit as an indication that the page should be cached on the SSD.The size of the hash table 410 may be a function of RAM and HDD size. Atsome point, the hash table 410 will likely hit its size limit, soaccessing new HDD blocks with the storage driver 222 can cause thestorage driver 222 to start pushing the oldest element(s) from the hash.Thereafter, reading from the blocks corresponding to those pushed outelements can be treated by the storage driver 222 as a “first hit”again.

The storage driver 222 can cache a page in RAM on the first hit. Thereis an in-memory cache where data can be kept so that if the page is hitthe second time (and so it has to be added to SSD) the storage driver222 does not have to re-read it from the HDD. The same cache can be usedto temporarily hold data of SSD blocks that are in the process ofrelocation. Thus, the memory cache can be used to store data for a pageafter the first hit so that the storage driver 222 does not have tore-read it during the second hit in order to write to the SSD. Theoutgoing SSD buffer 450, on the other hand, can be used by the storagedriver 222 to orchestrate writing data to SSD in relatively largechunks.

An issue with SSDs is that they typically erase data in chunks that aresignificantly larger than a 4 KB page. The internal SSD organizationinvolves pages (e.g., 512B-8 KB), which are joined into blocks (e.g.,˜512 KB-8 megabytes [MB]), which are then combined in planes. In manySSDs, an SSD page write can happen only to an erased SSD block, anderasing SSD blocks is typically a relatively slow process. This erasureproblem would be compounded if the storage driver 222 had to write 4 KBpages to the SSD on an individual basis. Hence, the outgoing SSD writebuffer 450 can be used to act as a staging buffer, to which data isadded when I/O hits the same page for the second time. This outgoing SSDwrite buffer 450 may be relatively small, such as 8 MB-16 MB, and may beused to group written pages together before actually flushing them toSSD. In contrast, the in-memory cache (which can hold cached page databefore a decision is made to flush it to SSD) may be much larger thanthat, such as several gigabytes (GBs). Thus, on the second hit of apage, the storage driver 222 can decide to add data for the page to theSSD. In making this decision, the storage driver 222 can either read thepage from the HDD (e.g., if the element's mem_cache_ptr is null—seeTable 1 below) or take the in-memory cache data and add it to theoutgoing SSD write buffer. When the outgoing SSD buffer 450 becomesfull, the storage driver 222 can flush it to the SSD.

The location pointer can initially point to null. The first node 420 isshown in FIG. 4 as also storing the device ID and page number, which canenable the storage driver 222 to resolve hash collisions if multipledevice IDs and page numbers are indexed to the same hash entry 412 ofthe hash table 410.

An LRU pointer is also stored in the first node 420 when the first hitor read of the page occurs. The LRU pointer can point to the LRU list430. The LRU list 430 can include a list of elements or pointers thatcan be used by the storage driver 222 in a least-recently used (LRU)caching algorithm. An operating principle behind the LRU cachingalgorithm can be that the least recently used or approximately leastrecently used element should no longer be cached. More frequently useddata elements can therefore be maintained in the cache. Thus, when thestorage driver 222 reads a page, the storage driver 222 can put areference to the page at the top or front of the LRU list 430,indicating that this page is the most frequently used page since it wasmost recently read. The storage driver 222 can later use the LRU list430 to determine which pages can be overwritten in the SSD 238 orin-memory cache 440, as will be described in greater detail below.

The LRU list 430 may be a linked list, doubly-linked list, vector,array, or the like and may have a fixed or variable size. Although LRUis an example caching algorithm described herein, other examples ofcaching algorithms may be used in its place, including such algorithmsas most recently used (MRU), pseudo LRU, random replacement, andadaptive replacement cache (ARC).

As described above, when a page is read just once it may not bedesirable to cache that page to the SSD 238. Thus, the location pointerin the first node 420 points to null, indicating that the page is notcached yet. Alternatively, the location pointer could point to thelocation of the page on the hard disk to indicate that the page is stillto be read from the hard disk if it is read again. Upon a second read ofthe page, the storage driver 222 can first look up the device ID andpage number in the hash table 410 to determine whether the locationpointer for the page points to null (or the hard disk), memory, or theSSD. Upon the second hit, the storage driver 222 can read the entry 412in the hash table, identify that the location pointer points to null (orto the hard disk), and would therefore know to access the page from thehard disk. In addition, the storage driver 222 can create a second node422 in the hash table pointed to by the first entry. The second node 422can be part of a linked list pointed to by the first node 420.

Once the second hit has occurred, it may be desirable to indicate thatthe page is eligible for caching in the SSD. Accordingly, the storagedriver 222 can create an indication that the page is ready for cachingby storing a reference or pointer to the page in the outgoing SSD buffer450. The storage driver 222 can also cache the page in memory in thein-memory cache 440 and store or update the location pointer to itslocation in RAM in the second node 422 of the hash table 410. Thus, whenthe storage driver 222 subsequently accesses the page number in the hashtable 410 a third time, traversing the linked list formed by nodes 420and 422, the storage driver 222 can determine that the page is locatedin memory by virtue of the location pointer to the in-memory cache 440.

As described above, it can be beneficial to accumulate a series ofreferences or pointers to pages so that pages are not writtenindividually to the SSD 238. The outgoing SSD buffer 450 is one exampleof a data structure that can be used to accumulate these references topages. The outgoing SSD buffer 450 may be in the form of a linked listor some other data structure. As shown, entries 452 in the outgoing SSDbuffer 450 include references or pointers to different pages that havebeen accessed at least twice (in one embodiment) by the storage driver222. As an alternative to storing pointers in the outgoing SSD buffer450, the device ID and page number for each page may be stored instead,which may also be considered storing references to the page in thebuffer 450.

Once the outgoing SSD buffer 450 is full, the storage driver 222 canflush the buffer 450 to the SSD 238. Flushing the buffer can entailwriting the actual page corresponding to each referenced page in thebuffer to the SSD 238 and removing the references to those pages fromthe buffer 450. Once a page has been stored or written to the SSD 238,it may be useful to remove the page from the in-memory cache 440 or tootherwise indicate that that memory is available for being overwrittenwith a different page. Accordingly, the location pointer in the hashentry 412 for a page can be updated by the storage driver 222 to pointto the page's location on the SSD 238 as shown by node 424. Thus, on athird hit or third read of the page, the storage driver 222 candetermine that the storage location pointer points to the SSD 238, andthen can access the page in its location stored on the SSD 238.

Each time the storage driver 222 reads or hits a page, the LRU pointerin the hash table entry 412 can be updated to move the page element orreference to the page element to the top or front of the LRU. When pageshave been in the LRU for a long time or are otherwise pushed to the endof the LRU (even in a relatively short amount of time), such pages maybe removed from the hash table 410. Accordingly, such pages may becandidates for removal or overwriting from either the in-memory cache440 or the SSD 238, wherever they are located. In one embodiment, allthe hash elements 412 can be independently linked in one hash LRU list,meaning that no matter what hash bucket a hash element belongs to, thereis just one hash LRU list that spans all of the elements in the entirehash table 410. So when a new element is added to bucket 1 of the hashtable 410, for example, this addition can potentially push out anelement from the last bucket in the hash table 410 because thatparticular element may reside at the bottom of the LRU. Reference to the“last bucket” herein need not refer to the last physical location of thehash table in memory, although it may. Rather, “last bucket” can referto the last bucket in the least-recently used (LRU) sense, or the lastelement pointed to in the hash table's 410 linked list of LRU pointers.

Although drawn separately for conceptual purposes, the hash table 410and the LRU 430 are not separate data structures in some embodiments(although they may be). Rather, the hash table 410 and LRU 430 may beone collection of elements that correspond to different pages of the HDDdevice and that may point to cached data in memory or on SSD. Theelements in the hash table 410 can be linked in hash buckets, andadditionally the very same elements can be present in the LRU list 430.When a page I/O is seen, the device's ID and page's offset can be usedto compute the hash bucket index (as described above) and then accessthe particular hash bucket short list to get to the corresponding hashelement. This access mechanism can constitute one interface foraccessing the data in the hash table 410, or a first hash accessinterface. A second interface to the data in the hash table 410 can bean LRU interface, where the storage driver 222 can traverse all elementsin the hash table 410 based on their last used time, or just pick theleast recently used element of all.

Below is an approximate description of what a hash element may look likein the hash table 410 (note that there may be at most one hash elementper given HDD page in some embodiments):

TABLE 1 Field Example Purpose bucket_next_link These two fields can puthash elements bucket_prev_link in doubly-linked hash bucket short lists.Given a device ID and a page number, the storage driver 222 can computean index of the corresponding hash bucket and then quickly traverse thelist to obtain the right hash element. Since the per-bucket lists areshort in some implementations, this does process is relatively fast.lru_next_link These two fields can allow hash elements lru_prev_link tobe combined into a separate LRU list that spans some or all elements insome or all buckets of the hash. In effect, any given hash element canend up being in two lists at the same time: the corresponding hashbucket short list, and the LRU list. mem_cache_ptr Pointer to thein-memory cache, if data for this hash element is also cached in memory.Can be null. ssd_offset Offset (or block number) indicating where on theSSD data for this hash element is stored. May be undefined (e.g.,−1) ifit is currently not stored on SSD. Can be changed to a new offset if thedata has to be overwritten because the SSD circular writing processmanaged to overwrite the entire SSD and loop back to the block that wastaken by this hash element.

The back pointer array 470 can maintain a mapping of storage locationson the SSD 238 for a given page to its hash entry 412 in the hash table410 so that the storage driver 222 can easily determine which portionsof the SSD can be overwritten. For example, the storage driver 222 maywish to overwrite a portion of the SSD 238 that has not been accessedrecently when caching to the SSD 238 and may look up that portion in theback pointer array 470. For each storage portion in the SSD 238 (such asa page or block of pages), the back pointer array 470 can point to alocation in the hash table 410. Traversing the linked list of one ormore nodes 420-424 in the hash entry 412 for a given page can allow thestorage driver 222 to identify the LRU pointer that is current for thepage. The storage driver 222 can then traverse the LRU pointer todetermine whether it points to null or to the last entry in the LRU, inwhich case the page may be ripe for overwriting. Otherwise, the page maynot be ripe for overwriting (unless perhaps no other page is availablewith a less recent entry in the LRU). Usage of the back pointer array470 is described in greater detail below with respect to FIG. 7.

The back pointers 470 can point directly to the hash elements, ratherthan to the hash table buckets. When a block in the SSD is about to beoverwritten, the storage driver 222 can use the array of back pointersin an attempt to get to the hash element. The storage driver 222 anaccess the array by taking the SSD block number and using it as anindex. If the back pointer in the array is null, it can mean that thecorresponding hash element has already been pushed out from memory, sothe SSD block may not be worth preserving and can be overwritten.Otherwise, the storage driver 222 can copy the block to a new locationon the SSD and can update the hash element to point to that newlocation. Although the hash element can be copied to a new location, thehash element may instead simply be placed in the in-memory cache and canbe flushed to a new SSD location a little later. The storage driver 222does not physically write relocated blocks to a new place on SSD rightaway in some cases because the storage driver 222 may already be busyflushing other data to the SSD.

Thus, the pointer that can be set to null is the back pointer in theback pointer array 470, which translates SSD blocks back to the hashentries in the hash table 410. Later when the circular SSD writingprocess gets to the corresponding blocks on the SSD, the storage driver222 can identify that the back pointer is null and so can overwrite theblock on SSD without trying to relocate it. Otherwise (if the backpointer is still valid and is still pointing to some hash element 420),the storage driver 222 can read the SSD block and add the SSD block tothe in-memory cache. The storage driver 222 can update the hash element420 to point to the in-memory cache.

In certain embodiments, back pointers are used so that the storagedriver 222 can relocate cached blocks on the SSD. When the circularwriting process gets to an already-used block (and the SSD is beingoverwritten circularly, meaning that the storage driver 222 may writeuntil the storage driver 222 hits the end, and then jump back to thebeginning of SSD), the storage driver 222 checks whether the backpointer is valid. If the back pointer is valid, the storage driver 222can read the current SSD contents and store them in memory, from wherethese contents will shortly be flushed to a new SSD location. Since thestorage driver 222 can track the almost overwritten data, the storagedriver 222 can update the mem_cache_ptr and ssd_offset (see Table 1above) in the hash element, and for that the storage driver 222 can usea pointer.

In certain embodiments, there is at most one hash element in the hashtable 410 per given page of an HDD. When a page is accessed for thefirst time by the storage driver 222 (meaning there is no correspondinghash element yet), the storage driver 222 can inject the element intothe hash table 410 and can use the element's mem_cache_ptr to point tothe page's data in the memory cache. When the page is accessed for thesecond time, the corresponding data can be written to SSD (and theelement's ssd_offset is set to point to the correct location on theSSD). In one embodiment, every time the storage driver 222 accesses ahash element, it moves the hash element to the top of the LRU list.

Turning to FIG. 5, an example initial caching process 500 is shown thatcan be implemented by the storage driver 222 or by equivalent hardwareor software in another device. The initial caching process 500 begins atblock 502 by receiving a page read request. The storage driver 222determines at block 504 whether an element exists in the hash table 410for this page. If so, the storage driver 222 executes an in-hash processat block 506, which is described below with respect to FIG. 6. If not,the storage driver 222 maps the page to a null hash entry 412 at block508, indicating that the page is on disk 236 or that it should beretrieved from disk next read. In one embodiment, the storage driver 222goes to the HDD on the second read if the second read occurs shortlyafter the first, for example, before there is time to insert the pageinto the in-memory cache. The in-memory cache may be several GBs insize; if the second hit happens before data cached by the first hit ispurged from the in-memory cache, that data can be used and added to theSSD outgoing buffer. If the second hit comes after that, the data mayneed to be reread from the HDD.

At block 510, the storage driver 222 obtains the page from the hard disk236 by reading the location on the hard disk 236 where the page isstored. At block 512, the storage driver 222 adds a reference to thepage to the top of the LRU list 430, and the process 500 ends. Thus, ifthe page was not already in the hash table 410, the process 500 resultsin storing an entry 412 in the hash table 410 for the page and does notyet actually cache the page. Alternatively, the process 500 may bemodified to cache the page in memory even upon a first read of the page.

As described above, if an entry 412 already existed in the hash table410 for the page read in FIG. 5, the in-hash process 600 at FIG. 6 maybe executed by the storage driver 222 (or other appropriate hardwareand/or software). The in-hash process 600 can enable the storage driver222 to locate where the page is stored, whether on the hard disk 236(pointed to by null), in memory 214, or on the SSD 238. The storagedriver 222 can also use the process 600 to cache a page to memory 214 orto the SSD 238 and then update the location of the page, e.g., byupdating the location pointer in the hash entry 412 described above withrespect to FIG. 4.

At block 602 of the in-hash process 600, the storage driver 222determines how the hash entry 412 (see block 504 of FIG. 5) is mapped.The hash entry 412 may be mapped to null, to memory 214, or to the SSD238 as described above with respect to FIG. 4. If the hash entry 412 ismapped to null, then at block 604 the storage driver 222 can retrievethe page from the hard disk. At block 605, the storage driver 222determines whether the in-memory cache 440 is full. If so, the storagedriver 222 proceeds to block 610, which will be described shortly. Ifnot, the storage driver 222 adds the page to in-memory cache 440 atblock 606 and maps the hash entry 412 for the page to the in-memorycache 440 at block 608. In addition, the storage driver 222 can move oradd a reference to the page to the top of the LRU list at block 608. Asdescribed above with respect to FIG. 4, the storage driver 222 canperform this mapping by creating a new linked node (e.g., 422) in theentry 412 for the page in the hash table 410. Alternatively, instead ofcreating a new linked list entry, a linked list need not be implemented.Instead, the storage driver 222 can update the existing entry 412 in thehash table to a point to a location in the in-memory cache 440 insteadof null.

At block 610, whether proceeding from block 608 or block 605, thestorage driver 222 can add a reference to the page to the outgoing SSDbuffer 450. At block 612, the storage driver 222 can determine whetherthe buffer 450 is full or whether the in-memory cache 440 is full. Ifnot, the process 600 ends. However, if so, the storage driver 222flushes the outgoing SSD buffer 450 to the SSD 238 at block 614. Moredetails of this step 614 are described below with respect to FIG. 7. Thestorage driver 222 may then map the hash entry 412 for each page in theoutgoing SSD buffer 450 to its location on the SSD 238 and free thememory cache or otherwise indicate that the entries of those pages inthe memory cache may be overwritten. Thus, the page may be cached to theSSD 238 if the outgoing SSD buffer 450 is full or if the in-memory cache440 is full.

If the in-memory cache 440 is full at the time that the page wouldordinarily be inserted into the in-memory cache 440, it can be cachedstraight to the SSD 238. Or, in another embodiment not shown, the pagemay be cached to the memory cache 440 instead of directly to the SSD238, but the memory cache 440 may first be flushed to the SSD 238 tomake room for the new page. Referring again to block 602, if the hashentry 412 for a page is mapped to memory, the storage driver 222 canretrieve the page from memory at block 618 and move or add a referenceto the page to the top of the LRU list 430 at block 620. At block 622,the storage driver 222 can optionally write the page to the SSD 238 andmap the hash entry 412 to the SSD 238. Alternatively, the storage driver222 can wait until the outgoing SSD buffer 450 or memory cache 440 havefilled before doing so.

Referring again to block 602, if the hash entry is mapped to the SSD238, the storage driver 222 can retrieve the page from the SSD 238 atblock 624 and move or add a reference to the top of the LRU list 430 atblock 626. As discussed above, in some embodiments the storage driver222 uses a single LRU to keep track of when a given page was accessed.This LRU can be used to prune elements from the hash (the storage driver222 does not hash every single page of the HDD in most embodiments, soat some point the elements may be removed), and also to keep the size ofin-memory cache under control. There is no need for a separate LRU forthe SSD in some implementations.

Turning to FIG. 7, an example embodiment of an SSD write process 700 isshown in which the storage driver 222 (or other hardware/software) cancache one or more pages to the SSD 238. At block 702, the storage driver222 receives pages to be written to the SSD 238 from the outgoing SSDbuffer 450. As mentioned above, writing to the SSD 238 may occur if theoutgoing SSD buffer 450 is full or if the memory cache 440 is full. Inother embodiments, writing may occur to the SSD 238 if a third hit to apage has occurred, at which time either just that page or the entireoutgoing SSD buffer 450 may be written to the SSD 238.

At block 704, it is determined by the storage driver 222 whether the SSD238 is full. If not, the storage driver 222 can write the pages to theSSD 238 in a circular fashion at block 718, such that blocks are notoverwritten. Otherwise, if the SSD is full at block 704, the storagedriver 222 identifies candidate pages to be overwritten at block 706. Asdescribed above, the storage driver 222 can overwrite the SSD incircles, using the back pointer array to determine whether eachblock-to-be-overwritten should be saved and/or relocated or overwritten.The pages that are candidates for being overwritten can include pagesthat were least recently used, oldest in time, or the like.

At block 708, the storage driver 222 looks up candidate pages in theback pointer array 470 to access the latest hash entry 412 for eachcandidate page. The storage driver 222 can then de-reference the LRUpointer in the hash entry 412 for each candidate page at block 710. Ifthe LRU pointer is null at block 712, or if it is the last LRU elementin the list or the least frequently used among other candidate pages,then the storage driver 222 can discard the candidate page from the SSD238 at block 716 and perform the write at block 718. Otherwise, if theLRU pointer is not null, the storage driver 222 can add the non-nullcandidate pages back to a new outgoing SSD buffer 450 at block 714and/or also to the in-memory cache 440. The outgoing SSD buffer 450 maytherefore be a double buffer containing a first buffer having a copy ofpages that are written to the SSD 238 and a second buffer that containspages to later be written to the SSD 238 that were just overwritten orabout to be overwritten on the SSD 238. In certain embodiments, theblocks that are about to be overwritten and that are to besaved/relocated are read from SSD and put back in the in-memory cache.They could have been put directly in the outgoing SSD write buffer, butthe storage driver 222 may be flushing this buffer at that moment, sothe storage driver 222 can put those blocks in the in-memory cacheinstead. Very soon the storage driver 222 can move these blocks to theoutgoing SSD write buffer by the cache pruning process.

Turning to FIG. 8, an example write I/O process is shown 800. The writeI/O process 800 can also be implemented by the storage driver 222 orother hardware and/or software. As described above, caching writeoperations may be less beneficial than caching reads. Writes aretypically either performed once on a data element and not performedagain or are performed multiple times on a data element periodically.Writes cached to a page once and then stored may not make sense to cachesince the page is only written to once and not written to again (withina long period of time). When writes are performed multiple times on adata element in a short period of time, those writes may be nativelycached in memory by the file system (in memory). Accordingly, there maybe no benefit to re-caching these writes to the SSD 238, since reads tosuch pages may be satisfied from the file system buffers that cache thewrites to those pages. However, as described above and other embodimentswrites may also be cached to the SSD.

At block 802, the storage driver 222 receives a page write request. Atblock 804, the storage driver 222 can determine whether the page maps tothe memory cache 440 or the SSD 238 in the page's hash entry 412. If so,the storage driver 222 can un-map the page from memory 440 or the SSD238, for example, by pointing the page to null. The process can thenproceed to block 808. Otherwise, from block 804, if the page is notmapped to memory 440 or SSD 238 in the hash table 410, the storagedriver can proceed to block 808, where the write is passed down to thehard disk 236.

Additional Example Embodiments

In certain embodiments, a system for caching can include a storagedriver including a hardware processor that can read a data element froma hard disk and cache the data element in a memory cache. The memorycache can have a size that is less than a size of a memory in which thememory cache is located. The storage driver can also store an indicationin the memory that the data element is to be cached in a solid-statedrive (SSD) without actually caching the data element in the SSD.Moreover, the storage driver can cache the data element in the SSD inresponse to the memory cache reaching its capacity or upon anothercondition, such as an outgoing SSD buffer reaching capacity.

The system of the preceding paragraph may be implemented together withany subcombination of the following features: the storage driver canalso store the indication that the data element is to be cachedsubsequent to reading the data element from the hard disk a second time;the memory cache can be an intermediate cache for the SSD; the storagedriver can also evict the data element from the memory in response tocaching the data element in the SSD; the storage driver may alsomaintain a data structure in the memory, where the data structure canmap the data element to a storage location in either the memory or theSSD; and the data structure can be a hash table indexed at least by dataelement identifiers.

In various embodiments, a system for caching can include a storagedriver that includes a hardware processor that can receive new dataelements to be cached to a solid state drive (SSD), where the SSD actsas a cache for a hard disk. The storage driver can also identify aportion of the SSD that is to be deleted to make room for the new dataelements. The portion may include cached data elements. The storagedriver may also access a data structure that stores characteristicsrelated to the cached data elements. These characteristics may beassociated with a caching algorithm. In response to the characteristicsindicating that first ones of the cached data elements are no longer tobe cached, the storage driver can delete the first cached data elementsfrom the portion of the SSD that is to be deleted. The storage drivercan also mark second ones of the cached data elements to be re-cached tothe SSD and delete the second cached data elements from the from theportion of the SSD that is to be deleted to produce a deleted portion ofthe SSD. The storage driver may also write the new data elements to theSSD in the deleted portion of the SSD. The storage driver may write thenew data elements to the SSD in a circular fashion.

Terminology

Conditional language, such as, among others, “can,” “could,” “might,” or“may,” unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or without userinput or prompting, whether these features, elements and/or steps areincluded or are to be performed in any particular embodiment.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including,” “having,” and the like are to be construed in aninclusive sense, as opposed to an exclusive or exhaustive sense; that isto say, in the sense of “including, but not limited to.” As used herein,the terms “connected,” “coupled,” or any variant thereof means anyconnection or coupling, either direct or indirect, between two or moreelements; the coupling or connection between the elements can bephysical, logical, or a combination thereof. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, refer to this application as a whole and not to anyparticular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, covers all of thefollowing interpretations of the word: any one of the items in the list,all of the items in the list, and any combination of the items in thelist. Likewise the term “and/or” in reference to a list of two or moreitems, covers all of the following interpretations of the word: any oneof the items in the list, all of the items in the list, and anycombination of the items in the list.

Depending on the embodiment, certain operations, acts, events, orfunctions of any of the algorithms described herein can be performed ina different sequence, can be added, merged, or left out altogether(e.g., not all are necessary for the practice of the algorithms).Moreover, in certain embodiments, operations, acts, functions, or eventscan be performed concurrently, e.g., through multi-threaded processing,interrupt processing, or multiple processors or processor cores or onother parallel architectures, rather than sequentially.

Systems and modules described herein may comprise software, firmware,hardware, or any combination(s) of software, firmware, or hardwaresuitable for the purposes described herein. Software and other modulesmay reside and execute on servers, workstations, personal computers,computerized tablets, PDAs, and other computing devices suitable for thepurposes described herein. Software and other modules may be accessiblevia local memory, via a network, via a browser, or via other meanssuitable for the purposes described herein. Data structures describedherein may comprise computer files, variables, programming arrays,programming structures, or any electronic information storage schemes ormethods, or any combinations thereof, suitable for the purposesdescribed herein. User interface elements described herein may compriseelements from graphical user interfaces, interactive voice response,command line interfaces, and other suitable interfaces.

Further, the processing of the various components of the illustratedsystems can be distributed across multiple machines, networks, and othercomputing resources. In addition, two or more components of a system canbe combined into fewer components. Various components of the illustratedsystems can be implemented in one or more virtual machines, rather thanin dedicated computer hardware systems and/or computing devices.Likewise, the data repositories shown can represent physical and/orlogical data storage, including, for example, storage area networks orother distributed storage systems. Moreover, in some embodiments theconnections between the components shown represent possible paths ofdata flow, rather than actual connections between hardware. While someexamples of possible connections are shown, any of the subset of thecomponents shown can communicate with any other subset of components invarious implementations.

Embodiments are also described above with reference to flow chartillustrations and/or block diagrams of methods, apparatus (systems) andcomputer program products. Each block of the flow chart illustrationsand/or block diagrams, and combinations of blocks in the flow chartillustrations and/or block diagrams, may be implemented by computerprogram instructions. Such instructions may be provided to a processorof a general purpose computer, special purpose computer,specially-equipped computer (e.g., comprising a high-performancedatabase server, a graphics subsystem, etc.) or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor(s) of the computer or other programmabledata processing apparatus, create means for implementing the actsspecified in the flow chart and/or block diagram block or blocks.

These computer program instructions may also be stored in anon-transitory computer-readable memory that can direct a computer orother programmable data processing apparatus to operate in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instruction meanswhich implement the acts specified in the flow chart and/or blockdiagram block or blocks. The computer program instructions may also beloaded onto a computing device or other programmable data processingapparatus to cause a series of operations to be performed on thecomputing device or other programmable apparatus to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide steps for implementingthe acts specified in the flow chart and/or block diagram block orblocks.

Any patents and applications and other references noted above, includingany that may be listed in accompanying filing papers, are incorporatedherein by reference. Aspects of the invention can be modified, ifnecessary, to employ the systems, functions, and concepts of the variousreferences described above to provide yet further implementations of theinvention.

These and other changes can be made to the invention in light of theabove Detailed Description. While the above description describescertain examples of the invention, and describes the best modecontemplated, no matter how detailed the above appears in text, theinvention can be practiced in many ways. Details of the system may varyconsiderably in its specific implementation, while still beingencompassed by the invention disclosed herein. As noted above,particular terminology used when describing certain features or aspectsof the invention should not be taken to imply that the terminology isbeing redefined herein to be restricted to any specific characteristics,features, or aspects of the invention with which that terminology isassociated. In general, the terms used in the following claims shouldnot be construed to limit the invention to the specific examplesdisclosed in the specification, unless the above Detailed Descriptionsection explicitly defines such terms. Accordingly, the actual scope ofthe invention encompasses not only the disclosed examples, but also allequivalent ways of practicing or implementing the invention under theclaims.

To reduce the number of claims, certain aspects of the invention arepresented below in certain claim forms, but the applicant contemplatesthe various aspects of the invention in any number of claim forms. Forexample, while only one aspect of the invention may be recited as ameans-plus-function claim under 35 U.S.C sec. 112(f) (AIA), otheraspects may likewise be embodied as a means-plus-function claim, or inother forms, such as being embodied in a computer-readable medium. Anyclaims intended to be treated under 35 U.S.C. § 112(f) will begin withthe words “means for”, but use of the term “for” in any other context isnot intended to invoke treatment under 35 U.S.C. § 112(f). Accordingly,the applicant reserves the right to pursue additional claims afterfiling this application, in either this application or in a continuingapplication.

What is claimed is:
 1. A data storage system for performing secondarycopy operations, the system comprising: a client computing deviceresiding in a primary storage subsystem and having at least one softwareapplication installed thereon, the client computing device associatedwith and in networked communication with a storage system located in theprimary storage subsystem, the storage system comprising a hard disk anda solid-state drive (SSD), the storage system configured to storeprimary data generated by the software application; a storage managerimplemented in a computing device and configured to instruct the clientcomputing device to perform tasks associated with one or more databackup operations in which the primary data is copied to one or moresecondary storage devices residing in a secondary storage subsystem tocreate one or more secondary copies having a different format than anative format of the primary data; a storage driver that controls SSDcache operations as part of performing storage operations which are partof the data backup operations, the storage driver implemented in ahardware processor residing within the primary storage subsystem andconfigured to: read a first data element from the hard disk; store afirst indication in memory that the first data element is to be cachedin the SSD without actually caching the first data element in the SSD;write the first data element to a buffer maintained in the memory; reada second data element from the hard disk; store a second indication inthe memory that the second data element is to be cached in the SSD;write the second data element to the buffer; subsequent to storage ofthe second indication in the memory, determine that the buffer hasreached capacity; and in response to determining that the buffer hasreached capacity: determine whether the SSD is at capacity; in responseto determining that the SSD is at capacity, access a data structure inthe memory, the data structure including entries corresponding tostorage locations on the SSD that store cached data elements, whereineach respective entry in the data structure is usable to locate in thememory first information indicative of how recently accessed was thecached data element stored in the storage location to which therespective entry corresponds; consult a plurality of entries in the datastructure to locate the first information associated with a plurality ofthe cached data elements, to identify one or more of the plurality ofdata elements as candidates to discard; discard one or more of thecandidates from the SSD; subsequent to discarding the one or morecandidates, write the first and second data elements from the buffer tothe SSD; and update the data structure in the memory to include entriescorresponding to the first and second data elements.
 2. The system ofclaim 1, wherein the first and second indication comprise pointers tothe first and second data elements.
 3. The system of claim 1, whereinthe storage driver is further configured to first cache the first andsecond data elements in a memory cache prior to caching the first andsecond data elements in the SSD.
 4. The system of claim 3, wherein thestorage driver is further configured to cache the first and second dataelements in the SSD in response to the memory cache reaching capacityeven if the buffer has not reached capacity.
 5. The system of claim 1,wherein the storage driver is further configured to evict the first dataelement from the SSD in response to receiving a write to the first dataelement.
 6. A method of performing data backup operations, comprising:with a storage manager implemented in a computing device, instructing aclient computing device residing in a primary storage subsystem toperform tasks associated with one or more data backup operations inwhich primary data generated by at least one software applicationexecuting on the client computing device is copied to one or moresecondary storage devices residing in a secondary storage subsystem tocreate one or more secondary copies having a different format than anative format of the primary data, the client computing deviceassociated with and in networked communication with a storage systemlocated in the primary storage subsystem, the storage system comprisinga hard disk and a solid-state drive (SSD) operating as a cache for thehard disk, the storage system configured to store primary data generatedby the software application; with a storage driver implemented in ahardware processor and that controls SSD cache operations as part ofperforming storage operations which are part of the data backupoperations: reading a first data element from the hard disk; storing afirst indication in memory that the first data element is to be cachedin the SSD without actually caching the first data element in the SSD;writing the first data element to a buffer maintained in the memory;reading a second data element from the hard disk; storing a secondindication in the memory that the second data element is to be cached inthe SSD; writing the second data element to the buffer; subsequent tostorage of the second indication in the memory, determining that thebuffer has reached capacity; and in response to determining that thebuffer has reached capacity: determining whether the SSD is at capacity;in response to determining that the SSD is at capacity, accessing a datastructure in the memory, the data structure including entriescorresponding to storage locations on the SSD that store cached dataelements, wherein each respective entry in the data structure is usableto locate in the memory information indicative of how recently accessedwas the cached data element stored in the storage location to which therespective entry corresponds; consulting a plurality of entries in thedata structure to locate the first information associated with aplurality of the cached data elements, to identify one or more of theplurality of data elements as candidates to discard; discarding one ormore of the candidates from the SSD; subsequent to said discarding theone or more candidates, writing the first and second data elements fromthe buffer to the SSD; and updating the data structure in the memory toinclude entries corresponding to the first and second data elements. 7.The method of claim 6, wherein the first and second indication comprisepointers to the first and second data elements.
 8. The method of claim6, further comprising first caching the first and second data elementsin a memory cache prior to caching the first and second data elements inthe SSD.
 9. The method of claim 8, further comprising caching the firstand second data elements in the SSD in response to the memory cachereaching capacity even if the buffer has not reached capacity.
 10. Themethod of claim 6, further comprising evicting the first data elementfrom the SSD in response to receiving a write to the first data element.